If you change WINDVD 4 installation directory from default C:\Program Files\InterVideo\WinDVD4 to a sub-directory of C:\Program Files\ (i.e. C:\Program Files\WinDVD4) you may have one or several instances of Windows Explorer which open at logon, in directory C:\Program Files\Common\Bin.
This is because WinnDVD 4 installation (I have not checked for other versions) creates a directory C:\Program Files\InterVideo\Common. If you change installation directory as per example above, then the common\ and common\bin\ directories are created in C:\Program Files\
Then you have in program files C:\Program Files\Common Files\ and C:\Program Files\Common\.
This creates a mess when Windows launches the applications listed in the registry in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run or HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run if any of these applications are located in C:\Program Files\Common Files\
This occurs for example for Norton Firewall which creates a Key SSC_UserPrompt = C:\Program Files\Common Files\Symantec Shared\Security Center\UsrPrmpt.exe
There are two workarounds :
1 - Completely uninstall Windvd 4 and reinstall to default directory
2 - Replace \Program Files\ with \Common~1\ in registry keys values i.e SSC_UserPrompt = C:\Program Files\Common~1\Symantec Shared\Security Center\UsrPrmpt.exe
As a matter of fact Explorer Opens in C:\Program Files\Common\ directory because it fails to find the application. Using Common~1 solves the problem.
However, my suggestion is to use workaround 1 !