Idle system should Auto logoff

We have a network with 250+ PCs connecting to several W2K servers on a WAN that uses Fiber and ISDN for connectivity. We want to set the PCs to automatically logoff the user after a period of inactivity instead of locking the system. All PCs are W2K or WXP. We tried to use the WinExit screen saver from MS but by default, it doesn’t force open Apps to close and log off the user. Since our users don’t have admin rights to the PC we’re looking for an ‘easy’ way to update the registry automatically using a .reg file to or an .inf file. We think we’ll have to use a runas command so the process will have Administrator privelege. We’re looking for help in creating the inf file or an alternative to our current plan.