Disable Shutting Down in Windows XP

You can prevent users from being able to shut down the computer. This might be useful in cases such as when you’re running a server and you don’t want anyone to shut it down inadvertently.

Navigate to:
HCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

And to:
HLM\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

In these locations, create or modify the DWORD value called NoClose and set it to 1. Reset it to 0 to enable shutting down.

Log out and Log back in, or restart Windows, for the change to take effect.