Re: need an idea...
If it's XP Pro I think there is a GPO that you can use to log them off after their "logon hours" expire.
Edit: couldn't find it. You could also create a batch file that will shut down the computer and set it in scheduled tasks to run at a certain time.
Change the world. Of one person. Today.
If your equation requires either a complex combination of variables to get the desired result OR you can't seem to get the result regardless of the variables....it ain't your variables, it's your constant.