I agree with the part about this being a Linux forum but, you don't have to look very far to see posts about Windows problems. Those questions are often dual boot type of questions and hopefully, this user will be inspired to use Linux also.
I looked through some old notes and came up with this diddy which is for Win Nt/2000. It may be of some use for XP but I don't have anything to try it on.
Note: Use caution when messing with the registry, Make backups and don't blame me for anything.
Completely Shutdown the Computer on NT/2000
When selecting shutdown on Windows NT/2000, the computer writes all unsaved data to disk, and then waits for the user to press the power button. This edit will immediately shut down the computer after writing the unsaved data to disk. The only problem is that this feature must be supported in your computers BIOS. The entry should already be there, but if it is not then you may add it.
Key: HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Windows NT/Currentversion/Winlogon
Data: 0=Disable 1=Enable
Data Type: REG_SZ