Auto logoff

I am looking for a way to make a Windows XP machine logoff after the user has not either moved the mouse or touched the keyboard for 20 minutes. Any suggestions on where I could get started, or if there is a script or program that already can do such a thing. Thanks.

 

Turn on the screen saver and set the on resume show welcome screen is the built in way, but it only set you to switch users. I don't think anything was included with windows because what if someone rushed away while some document was open they were working on? Windows tries to log them off its just gonna ask to save and sit there anyway. Anything else you would need a program that had a timer, ran as a service and detected mouse movement, issues a log off to windows, I am not sure if there is a way to do this without it prompting if you would like to log off for sure.