What is the boot sequence for Windows XP?

Posted on 2008-11-12
Last Modified: 2012-05-05
What is the boot sequence for XP?  I mean what is run or loaded when?  
Question by:glow060197
    LVL 16

    Accepted Solution

    Hi glow,

    1.  First is the POST, this stands for Power On Self Test, for the computer. This process tests memory as well as a number of other subsystems. You can usually monitor this as it runs each test. After that is complete the system will run POST for any device that has a BIOS (Basic Input-Output System). An AGP has its own BIOS, as do some network cards and various other devices.

    2. Once the POST is complete and the BIOS is sure that everything is working properly, the BIOS will then attempt to read the MBR (Master Boot Record). This is the first sector of the first hard drive (called the Master or HD0). When the MBR takes over it means that Windows is now in control.

    3. The MBR looks at the BOOT SECTOR (the first sector of the active partition). That is where NTLDR is located, NTLDR is the BOOT LOADER for Windows XP. NTLDR will allow memory addressing, initiate the file system, read the boot.ini and load the boot menu. NTLDR has to be in the root of the active partition as do NTDETECT.COM, BOOT.INI, BOOTSECT.DOS (for multi-OS booting) and NTBOOTDD.SYS (if you have SCSI adapters)

    4. Once XP is selected from the Boot Menu, NTLDR will run NTDETECT.COM, BOOT.INI and BOOTSECT.DOS to get the proper OS selected and loaded. The system starts in 16-bit real mode and then moves into 32-bit protected mode.

    5. NTLDR will then load NTOSKRNL.EXE and HAL.DLL. Effectively, these two files are windows XP. They must be located in %SystemRoot%System32.

    6. NTLDR reads the registry, chooses a hardware profile and authorizes device drivers, in that exact order.

    7. At this point NTOSKRNL.EXE takes over. It starts WINLOGON.EXE that in turn starts LSASS.EXE, this is the program that display the Logon screen so that you can logon.

    LVL 27

    Expert Comment

    glow ... if you wish to have a more detailed description then perhaps this article will suffice .. notice that there is a printer friendly version >

    Troubleshooting the Startup Process:

    Alternatively you may prefer a more basic approach, with graphics >

    The PC Boot Process - Windows XP:

    Author Comment


    >>5. NTLDR will then load NTOSKRNL.EXE and HAL.DLL. Effectively, these two files are windows XP.     >> They must be located in %SystemRoot%System32.

    Just curious...what would happen if they weren't there or were corrupted??
    LVL 16

    Expert Comment

    Windows will not start.

    "Windows could not start because the following file is missing or corrupt:

    <Windows root>\system32\ntoskrnl.exe.
    Please reinstall a copy of the above file. "

    Author Closing Comment

    thanks, my friend.

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