Need code to get Computer Name from NT Registry

Thanks, you're answer was right on target!

Do you know a good book or web site that might detail many registry calls?  For example, to get the HOST name instead of the computer, to get the IP Address, currently logged in user, and various other things like that?  Just for my future reference...  (and up'ed the point value of the question to 150, so please post the info if you've got it...)

 Sorry but I don't... I can post the API functions related to the registry management if U want... :)

Sure, if you don't mind.  Thanks.

This has been taken from the MSDN. There are some others, but these are the most common used.
First of all you've got a description of each function, and in the end a sample. Good luck!

Note: Do not panic! Even though the parameters info it's in C, you can find the VB data types
in API Text Viewer.

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RegCloseKey
The RegCloseKey function releases a handle to the specified key.

LONG RegCloseKey(
  HKEY hKey   // handle to key to close
);
 
Parameters
hKey
Handle to the open key to close.
Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
The handle for a specified key should not be used after it has been closed, because it will no longer be valid. Key handles should not be left open any longer than necessary.

The RegCloseKey function does not necessarily write information to the registry before returning; it can take as much as several seconds for the cache to be flushed to the hard disk. If an application must explicitly write registry information to the hard disk, it can use the RegFlushKey function. RegFlushKey, however, uses many system resources and should be called only when necessary.

Windows CE: The RegCloseKey function always writes information to the registry before returning, eliminating the need to flush keys in the Windows CE registry.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.

See Also
Registry Overview, Registry Functions, RegCreateKey, RegCreateKeyEx, RegDeleteKey, RegFlushKey, RegOpenKey, RegOpenKeyEx, RegSetValue, RegSetValueEx

 
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RegCreateKeyEx
The RegCreateKeyEx function creates the specified key. If the key already exists in the registry, the function opens it.

LONG RegCreateKeyEx(
  HKEY hKey,                // handle to an open key
  LPCTSTR lpSubKey,         // address of subkey name
  DWORD Reserved,           // reserved
  LPTSTR lpClass,           // address of class string
  DWORD dwOptions,          // special options flag
  REGSAM samDesired,        // desired security access
  LPSECURITY_ATTRIBUTES lpSecurityAttributes,
                            // address of key security structure
  PHKEY phkResult,          // address of buffer for opened handle
  LPDWORD lpdwDisposition   // address of disposition value buffer
);
 
Parameters
hKey
Handle to a currently open key or one of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

The key opened or created by the RegCreateKeyEx function is a subkey of the key identified by the hKey parameter.

lpSubKey
Pointer to a null-terminated string specifying the name of a subkey that this function opens or creates. The subkey specified must be a subkey of the key identified by the hKey parameter. This subkey must not begin with the backslash character ('\'). This parameter cannot be NULL.
Reserved
Reserved; must be zero.
lpClass
Pointer to a null-terminated string that specifies the class (object type) of this key. This parameter is ignored if the key already exists.
dwOptions
Specifies special options for the key. This parameter can be one of the following values. Value Meaning
REG_OPTION_NON_VOLATILE This key is not volatile; this is the default. The information is stored in a file and is preserved when the system is restarted. The RegSaveKey function saves keys that are not volatile.  
REG_OPTION_VOLATILE Windows NT: This key is volatile; the information is stored in memory and is not preserved when the system is restarted. The RegSaveKey function does not save volatile keys. This flag is ignored if the key already exists.
Windows 95: This value is ignored. If REG_OPTION_VOLATILE is specified, the RegCreateKeyEx function creates a nonvolatile key and returns ERROR_SUCCESS.
 
REG_OPTION_BACKUP_RESTORE  Windows NT: If this flag is set, the function ignores the samDesired parameter and attempts to open the key with the access required to backup or restore the key. If the calling thread has the SE_BACKUP_NAME privilege enabled, the key is opened with ACCESS_SYSTEM_SECURITY and KEY_READ access. If the calling thread has the SE_RESTORE_NAME privilege enabled, the key is opened with ACCESS_SYSTEM_SECURITY and KEY_WRITE access. If both privileges are enabled, the key has the combined accesses for both privileges.  


samDesired
Specifies an access mask that specifies the desired security access for the new key. This parameter can be a combination of the following values: Value Meaning
KEY_ALL_ACCESS Combination of KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, KEY_NOTIFY, KEY_CREATE_SUB_KEY, KEY_CREATE_LINK, and KEY_SET_VALUE access.
KEY_CREATE_LINK Permission to create a symbolic link.
KEY_CREATE_SUB_KEY Permission to create subkeys.
KEY_ENUMERATE_SUB_KEYS Permission to enumerate subkeys.
KEY_EXECUTE Permission for read access.
KEY_NOTIFY Permission for change notification.
KEY_QUERY_VALUE Permission to query subkey data.
KEY_READ Combination of KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, and KEY_NOTIFY access.
KEY_SET_VALUE Permission to set subkey data.
KEY_WRITE Combination of KEY_SET_VALUE and KEY_CREATE_SUB_KEY access.


lpSecurityAttributes
Pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpSecurityAttributes is NULL, the handle cannot be inherited.
Windows NT: The lpSecurityDescriptor member of the structure specifies a security descriptor for the new key. If lpSecurityAttributes is NULL, the key gets a default security descriptor.

phkResult
Pointer to a variable that receives a handle to the opened or created key. When you no longer need the returned handle, call the RegCloseKey function to close it.
lpdwDisposition
Pointer to a variable that receives one of the following disposition values: Value Meaning
REG_CREATED_NEW_KEY The key did not exist and was created.
REG_OPENED_EXISTING_KEY The key existed and was simply opened without being changed.


Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
The key that the RegCreateKeyEx function creates has no values. An application can use the RegSetValue or RegSetValueEx function to set key values.

The key identified by the hKey parameter must have been opened with KEY_CREATE_SUB_KEY access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function.

An application cannot create a key under HKEY_USERS or HKEY_LOCAL_MACHINE.

An application can use RegCreateKeyEx to temporarily lock a portion of the registry. When the locking process creates a new key, it receives the disposition value REG_CREATED_NEW_KEY, indicating that it "owns" the lock. Another process attempting to create the same key receives the disposition value REG_OPENED_EXISTING_KEY, indicating that another process already owns the lock.

Windows CE: The dwOptions and samDesired parameters are ignored and should be set to zero to ensure compatibility with future versions of Windows CE.

The lpSecurityAttributes parameter should be set to NULL. Windows CE automatically assigns the key a default security descriptor.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions, RegCloseKey, RegCreateKey, RegDeleteKey, RegOpenKey, RegOpenKeyEx, RegSaveKey, SECURITY_ATTRIBUTES

 
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RegDeleteKey
Windows 95: The RegDeleteKey function deletes a subkey and all its descendants.

Windows NT: The RegDeleteKey function deletes the specified subkey. The subkey to be deleted must not have subkeys.

LONG RegDeleteKey(
  HKEY hKey,         // handle to open key
  LPCTSTR lpSubKey   // address of name of subkey to delete
);
 
Parameters
hKey
Handle to a currently open key or one of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

The key specified by the lpSubKey parameter must be a subkey of the key identified by hKey.

lpSubKey
Pointer to a null-terminated string specifying the name of the key to delete. This parameter cannot be NULL.
Windows NT: The specified key must not have subkeys.

Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
If the function succeeds, RegDeleteKey removes the specified key from the registry. The entire key, including all of its values, is removed.

To open the key, use the RegCreateKeyEx or RegOpenKeyEx function. Do not use the RegCreateKey or RegOpenKey functions.

Windows CE: With Windows CE, you can not RegDeleteKey a key which an application currently has open.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions, RegCloseKey, RegCreateKeyEx, RegOpenKeyEx

 
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RegDeleteValue
The RegDeleteValue function removes a named value from the specified registry key.

LONG RegDeleteValue(
  HKEY hKey,            // handle to key
  LPCTSTR lpValueName   // address of value name
);
 
Parameters
hKey
Handle to a currently open key or any of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

lpValueName
Pointer to a null-terminated string that names the value to remove. If this parameter is NULL or points to an empty string, the value set by the RegSetValue function is removed.
Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
The key identified by the hKey parameter must have been opened with KEY_SET_VALUE access (KEY_WRITE access includes KEY_SET_VALUE access).

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions, RegSetValue, RegSetValueEx

 
------------------------------------------------------------------
RegEnumKeyEx
The RegEnumKeyEx function enumerates subkeys of the specified open registry key. The function retrieves information about one subkey each time it is called. Unlike the RegEnumKey function, RegEnumKeyEx retrieves the class name of the subkey and the time it was last modified.

LONG RegEnumKeyEx(
  HKEY hKey,          // handle to key to enumerate
  DWORD dwIndex,      // index of subkey to enumerate
  LPTSTR lpName,      // address of buffer for subkey name
  LPDWORD lpcbName,   // address for size of subkey buffer
  LPDWORD lpReserved, // reserved
  LPTSTR lpClass,     // address of buffer for class string
  LPDWORD lpcbClass,  // address for size of class buffer
  PFILETIME lpftLastWriteTime
                      // address for time key last written to
);
 
Parameters
hKey
Handle to a currently open key or one of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

The enumerated keys are subkeys of the key identified by hKey.

dwIndex
Specifies the index of the subkey to retrieve. This parameter should be zero for the first call to the RegEnumKeyEx function and then incremented for subsequent calls.
Because subkeys are not ordered, any new subkey will have an arbitrary index. This means that the function may return subkeys in any order.

lpName
Pointer to a buffer that receives the name of the subkey, including the terminating null character. The function copies only the name of the subkey, not the full key hierarchy, to the buffer.
lpcbName
Pointer to a variable that specifies the size, in characters, of the buffer specified by the lpName parameter. This size should include the terminating null character. When the function returns, the variable pointed to by lpcbName contains the number of characters stored in the buffer. The count returned does not include the terminating null character.
lpReserved
Reserved; must be NULL.
lpClass
Pointer to a buffer that contains the class of the enumerated subkey when the function returns. This parameter can be NULL if the class is not required.
lpcbClass
Pointer to a variable that specifies the size, in characters, of the buffer specified by the lpClass parameter. The size should include the terminating null character. When the function returns, lpcbClass contains the number of characters stored in the buffer. The count returned does not include the terminating null character. This parameter can be NULL only if lpClass is NULL.
lpftLastWriteTime
Pointer to a variable that receives the time the enumerated subkey was last written to.
Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
To enumerate subkeys, an application should initially call the RegEnumKeyEx function with the dwIndex parameter set to zero. The application should then increment the dwIndex parameter and call RegEnumKeyEx until there are no more subkeys (until the function returns ERROR_NO_MORE_ITEMS).

The application can also set dwIndex to the index of the last subkey on the first call to the function and decrement the index until the subkey with the index 0 is enumerated. To retrieve the index of the last subkey, use the RegQueryInfoKey function.

While an application is using the RegEnumKeyEx function, it should not make calls to any registration functions that might change the key being enumerated.

The key identified by hKey must have been opened with KEY_ENUMERATE_SUB_KEYS access (KEY_READ includes KEY_ENUMERATE_SUB_KEYS). Use the RegCreateKeyEx or RegOpenKeyEx function to open the key.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions, RegCreateKeyEx, RegDeleteKey, RegEnumKey, RegOpenKeyEx, RegQueryInfoKey

 
----------------------------------------------------------------------
RegEnumValue
The RegEnumValue function enumerates the values for the specified open registry key. The function copies one indexed value name and data block for the key each time it is called.

LONG RegEnumValue(
  HKEY hKey,              // handle to key to query
  DWORD dwIndex,          // index of value to query
  LPTSTR lpValueName,     // address of buffer for value string
  LPDWORD lpcbValueName,  // address for size of value buffer
  LPDWORD lpReserved,     // reserved
  LPDWORD lpType,         // address of buffer for type code
  LPBYTE lpData,          // address of buffer for value data
  LPDWORD lpcbData        // address for size of data buffer
);
 
Parameters
hKey
Handle to a currently open key or one of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

The enumerated values are associated with the key identified by hKey.

dwIndex
Specifies the index of the value to retrieve. This parameter should be zero for the first call to the RegEnumValue function and then be incremented for subsequent calls.
Because values are not ordered, any new value will have an arbitrary index. This means that the function may return values in any order.

lpValueName
Pointer to a buffer that receives the name of the value, including the terminating null character.
lpcbValueName
Pointer to a variable that specifies the size, in characters, of the buffer pointed to by the lpValueName parameter. This size should include the terminating null character. When the function returns, the variable pointed to by lpcbValueName contains the number of characters stored in the buffer. The count returned does not include the terminating null character.
lpReserved
Reserved; must be NULL.
lpType
Pointer to a variable that receives the type code for the value entry. The type code can be one of the following values: Value Meaning
REG_BINARY Binary data in any form.
REG_DWORD A 32-bit number.
REG_DWORD_LITTLE_ENDIAN A 32-bit number in little-endian format. This is equivalent to REG_DWORD.
In little-endian format, a multi-byte value is stored in memory from the lowest byte (the "little end") to the highest byte. For example, the value 0x12345678 is stored as (0x78 0x56 0x34 0x12) in little-endian format.

Windows NT, Windows 95, and Windows 98 are designed to run on little-endian computer architectures. A user may connect to computers that have big-endian architectures, such as some UNIX systems.
 
REG_DWORD_BIG_ENDIAN A 32-bit number in big-endian format.
In big-endian format, a multi-byte value is stored in memory from the highest byte (the "big end") to the lowest byte. For example, the value 0x12345678 is stored as (0x12 0x34 0x56 0x78) in big-endian format.
 
REG_EXPAND_SZ A null-terminated string that contains unexpanded references to environment variables (for example, "%PATH%"). It will be a Unicode or ANSI string depending on whether you use the Unicode or ANSI functions. To expand the environment variable references, use theExpandEnvironmentStrings function.
REG_LINK A Unicode symbolic link.
REG_MULTI_SZ An array of null-terminated strings, terminated by two null characters.
REG_NONE No defined value type.
REG_RESOURCE_LIST A device-driver resource list.
REG_SZ A null-terminated string. It will be a Unicode or ANSI string, depending on whether you use the Unicode or ANSI functions.


The lpType parameter can be NULL if the type code is not required.

lpData
Pointer to a buffer that receives the data for the value entry. This parameter can be NULL if the data is not required.
lpcbData
Pointer to a variable that specifies the size, in bytes, of the buffer pointed to by the lpData parameter. When the function returns, the variable pointed to by the lpcbData parameter contains the number of bytes stored in the buffer. This parameter can be NULL, only if lpData is NULL.
Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
To enumerate values, an application should initially call the RegEnumValue function with the dwIndex parameter set to zero. The application should then increment dwIndex and call the RegEnumValue function until there are no more values (until the function returns ERROR_NO_MORE_ITEMS).

The application can also set dwIndex to the index of the last value on the first call to the function and decrement the index until the value with index 0 is enumerated. To retrieve the index of the last value, use the RegQueryInfoKey function.

While using RegEnumValue, an application should not call any registration functions that might change the key being queried.

The key identified by the hKey parameter must have been opened with KEY_QUERY_VALUE access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function.

To determine the maximum size of the name and data buffers, use the RegQueryInfoKey function.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions, RegCreateKeyEx, RegEnumKey, RegEnumKeyEx, RegOpenKeyEx, RegQueryInfoKey

 
----------------------------------------------------------------------
RegOpenKeyEx
The RegOpenKeyEx function opens the specified key.

LONG RegOpenKeyEx(
  HKEY hKey,         // handle to open key
  LPCTSTR lpSubKey,  // address of name of subkey to open
  DWORD ulOptions,   // reserved
  REGSAM samDesired, // security access mask
  PHKEY phkResult    // address of handle to open key
);
 
Parameters
hKey
Handle to a currently open key or any of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

lpSubKey
Pointer to a null-terminated string containing the name of the subkey to open. If this parameter is NULL or a pointer to an empty string, the function will open a new handle to the key identified by the hKey parameter. In this case, the function will not close the handles previously opened.
ulOptions
Reserved; must be zero.
samDesired
Specifies an access mask that describes the desired security access for the new key. This parameter can be a combination of the following values: Value Meaning
KEY_ALL_ACCESS Combination of KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, KEY_NOTIFY, KEY_CREATE_SUB_KEY, KEY_CREATE_LINK, and KEY_SET_VALUE access.
KEY_CREATE_LINK Permission to create a symbolic link.
KEY_CREATE_SUB_KEY Permission to create subkeys.
KEY_ENUMERATE_SUB_KEYS Permission to enumerate subkeys.
KEY_EXECUTE Permission for read access.
KEY_NOTIFY Permission for change notification.
KEY_QUERY_VALUE Permission to query subkey data.
KEY_READ Combination of KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, and KEY_NOTIFY access.
KEY_SET_VALUE Permission to set subkey data.
KEY_WRITE Combination of KEY_SET_VALUE and KEY_CREATE_SUB_KEY access.


phkResult
Pointer to a variable that receives a handle to the opened key. When you no longer need the returned handle, call the RegCloseKey function to close it.
Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
Unlike the RegCreateKeyEx function, the RegOpenKeyEx function does not create the specified key if the key does not exist in the registry.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions, RegCloseKey, RegCreateKeyEx, RegDeleteKey, RegOpenKey

 
-----------------------------------------------------------------------
RegQueryValueEx
The RegQueryValueEx function retrieves the type and data for a specified value name associated with an open registry key.

LONG RegQueryValueEx(
  HKEY hKey,           // handle to key to query
  LPTSTR lpValueName,  // address of name of value to query
  LPDWORD lpReserved,  // reserved
  LPDWORD lpType,      // address of buffer for value type
  LPBYTE lpData,       // address of data buffer
  LPDWORD lpcbData     // address of data buffer size
);
 
Parameters
hKey
Handle to a currently open key or any of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

lpValueName
Pointer to a null-terminated string containing the name of the value to query.
If lpValueName is NULL or an empty string, "", the function retrieves the type and data for the key's unnamed or default value, if any.

Windows 95 and Windows 98: Every key has a default value that initially does not contain data. On Windows 95, the default value type is always REG_SZ. On Windows 98, the type of a key's default value is initially REG_SZ, but RegSetValueEx can specify a default value with a different type.

Windows NT: Keys do not automatically have an unnamed or default value. Unnamed values can be of any type.

lpReserved
Reserved; must be NULL.
lpType
Pointer to a variable that receives the type of data associated with the specified value. The value returned through this parameter will be one of the following: Value Meaning
REG_BINARY Binary data in any form.
REG_DWORD A 32-bit number.
REG_DWORD_LITTLE_ENDIAN A 32-bit number in little-endian format. This is equivalent to REG_DWORD.
In little-endian format, a multi-byte value is stored in memory from the lowest byte (the "little end") to the highest byte. For example, the value 0x12345678 is stored as (0x78 0x56 0x34 0x12) in little-endian format.

Windows NT, Windows 95, and Windows 98 are designed to run on little-endian computer architectures. A user may connect to computers that have big-endian architectures, such as some UNIX systems.
 
REG_DWORD_BIG_ENDIAN A 32-bit number in big-endian format.
In big-endian format, a multi-byte value is stored in memory from the highest byte (the "big end") to the lowest byte. For example, the value 0x12345678 is stored as (0x12 0x34 0x56 0x78) in big-endian format.
 
REG_EXPAND_SZ A null-terminated string that contains unexpanded references to environment variables (for example, "%PATH%"). It will be a Unicode or ANSI string depending on whether you use the Unicode or ANSI functions. To expand the environment variable references, use theExpandEnvironmentStrings function.
REG_LINK A Unicode symbolic link.
REG_MULTI_SZ An array of null-terminated strings, terminated by two null characters.
REG_NONE No defined value type.
REG_RESOURCE_LIST A device-driver resource list.
REG_SZ A null-terminated string. It will be a Unicode or ANSI string depending on whether you use the Unicode or ANSI functions.


The lpType parameter can be NULL if the type is not required.

lpData
Pointer to a buffer that receives the value's data. This parameter can be NULL if the data is not required.
lpcbData
Pointer to a variable that specifies the size, in bytes, of the buffer pointed to by the lpData parameter. When the function returns, this variable contains the size of the data copied to lpData.
If the data has the REG_SZ, REG_MULTI_SZ or REG_EXPAND_SZ type, then lpcbData will also include the size of the terminating null character.

The lpcbData parameter can be NULL only if lpData is NULL.

If the buffer specified by lpData parameter is not large enough to hold the data, the function returns the value ERROR_MORE_DATA, and stores the required buffer size, in bytes, into the variable pointed to by lpcbData.

If lpData is NULL, and lpcbData is non-NULL, the function returns ERROR_SUCCESS, and stores the size of the data, in bytes, in the variable pointed to by lpcbData. This lets an application determine the best way to allocate a buffer for the value's data.

Window NT: If hKey specifies HKEY_PERFORMANCE_DATA and the lpData buffer is too small, RegQueryValueEx returns ERROR_MORE_DATA but lpcbData does not return the required buffer size. This is because the size of the performance data can change from one call to the next. In this case, you must increase the buffer size and call RegQueryValueEx again passing the updated buffer size in the lpcbData parameter. Repeat this until the function succeeds. You need to maintain a separate variable to keep track of the buffer size, because the value returned by lpcbData is unpredictable.

Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
The key identified by hKey must have been opened with KEY_QUERY_VALUE access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function.

If the value data has the REG_SZ, REG_MULTI_SZ or REG_EXPAND_SZ type, and the ANSI version of this function is used (either by explicitly calling RegQueryValueExA or by not defining UNICODE before including the WINDOWS.H file), this function converts the stored Unicode string to an ANSI string before copying it to the buffer pointed to by lpData.

Window NT: When calling the RegQueryValueEx function with hKey set to the HKEY_PERFORMANCE_DATA handle and a value string of a specified object, the returned data structure sometimes has unrequested objects. Don't be surprised; this is normal behavior. When calling the RegQueryValueEx function, you should always expect to walk the returned data structure to look for the requested object.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions,ExpandEnvironmentStrings, RegCreateKeyEx, RegEnumKey, RegEnumKeyEx, RegEnumValue, RegOpenKeyEx, RegQueryInfoKey, RegQueryValue

 
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RegSetValueEx
The RegSetValueEx function sets the data and type of a specified value under a registry key.

LONG RegSetValueEx(
  HKEY hKey,           // handle to key to set value for
  LPCTSTR lpValueName, // name of the value to set
  DWORD Reserved,      // reserved
  DWORD dwType,        // flag for value type
  CONST BYTE *lpData,  // address of value data
  DWORD cbData         // size of value data
);
 
Parameters
hKey
Handle to a currently open key or any of the following predefined reserved handle values:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

lpValueName
Pointer to a string containing the name of the value to set. If a value with this name is not already present in the key, the function adds it to the key.
If lpValueName is NULL or an empty string, "", the function sets the type and data for the key's unnamed or default value.

Windows 95 and Windows 98: On Windows 95, the type of a key's default value is always REG_SZ, so the dwType parameter must specify REG_SZ for an unnamed value. On Windows 98, an unnamed value can be of any type.

Windows NT: Registry keys do not have default values, but they can have one unnamed value, which can be of any type.

Reserved
Reserved; must be zero.
dwType
Specifies the type of information to be stored as the value's data. This parameter can be one of the following values: Value Meaning
REG_BINARY Binary data in any form.
REG_DWORD A 32-bit number.
REG_DWORD_LITTLE_ENDIAN A 32-bit number in little-endian format. This is equivalent to REG_DWORD.
In little-endian format, a multi-byte value is stored in memory from the lowest byte (the "little end") to the highest byte. For example, the value 0x12345678 is stored as (0x78 0x56 0x34 0x12) in little-endian format.

Windows NT, Windows 95, and Windows 98 are designed to run on little-endian computer architectures. A user may connect to computers that have big-endian architectures, such as some UNIX systems.
 
REG_DWORD_BIG_ENDIAN A 32-bit number in big-endian format.
In big-endian format, a multi-byte value is stored in memory from the highest byte (the "big end") to the lowest byte. For example, the value 0x12345678 is stored as (0x12 0x34 0x56 0x78) in big-endian format.
 
REG_EXPAND_SZ A null-terminated string that contains unexpanded references to environment variables (for example, "%PATH%"). It will be a Unicode or ANSI string depending on whether you use the Unicode or ANSI functions. To expand the environment variable references, use theExpandEnvironmentStrings function.
REG_LINK A Unicode symbolic link.
REG_MULTI_SZ An array of null-terminated strings, terminated by two null characters.
REG_NONE No defined value type.
REG_RESOURCE_LIST A device-driver resource list.
REG_SZ A null-terminated string. It will be a Unicode or ANSI string depending on whether you use the Unicode or ANSI functions.
Do not use the REG_SZ type to store hard-coded paths to the system root directory or to the drive containing the system files. Instead, use the REG_EXPAND_SZ type with environment variables such as "%SystemRoot%". This ensures that the path will be up-to-date even if the user remaps the system drive to a different drive letter.
 


lpData
Pointer to a buffer containing the data to be stored with the specified value name.
cbData
Specifies the size, in bytes, of the information pointed to by the lpData parameter. If the data is of type REG_SZ, REG_EXPAND_SZ, or REG_MULTI_SZ, cbData must include the size of the terminating null character.
Return Values
If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in WINERROR.H. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks
Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the filenames stored in the registry. This helps the registry perform efficiently. Application elements such as icons, bitmaps, and executable files should be stored as files and not be placed in the registry.

The key identified by the hKey parameter must have been opened with KEY_SET_VALUE access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function.

If dwType is the REG_SZ, REG_MULTI_SZ or REG_EXPAND_SZ type and the ANSI version of this function is used (either by explicitly calling RegSetValueExA or by not defining UNICODE before including the WINDOWS.H file), the data pointed to by the lpData parameter must be an ANSI character string. The string is converted to Unicode before it is stored in the registry.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also
Registry Overview, Registry Functions, RegCreateKeyEx, RegFlushKey, RegOpenKeyEx, RegQueryValue, RegQueryValueEx, RegSetValue

 
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Sample:

This shows a list of printers.

    Dim ft As FILETIME
    Dim keyhandle& 'it has the same effect that dim keyhandle as long
    Dim res&
    Dim curidx&
    Dim keyname$, classname$ 'it has the same effect that dim keyname as string
    Dim keylen&, classlen&
    Dim msg$
    Dim reserved&
    res& = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SYSTEM\CurrentControlSet\Control\Print\Printers", 0, KEY_READ, keyhandle)
    If res <> ERROR_SUCCESS Then
        MsgBox "Can't open key"
        Exit Sub
    End If
    Do
        keylen& = 2000
        classlen& = 2000
        keyname$ = String$(keylen, 0)
        classname$ = String$(classlen, 0)
        res = RegEnumKeyEx(keyhandle, curidx, keyname$, keylen, reserved, classname$, classlen, ft)
        curidx = curidx + 1
        If res = ERROR_SUCCESS Then msg$ = msg$ & Left$(keyname$, keylen) + vbCrLf
    Loop While res = ERROR_SUCCESS
   
    Call RegCloseKey(keyhandle)
    MsgBox msg$, 0, "Printers"