Auto-Logoff Users with Roaming Profiles

Hello-

I know there is a way to use Scheduled Tasks to auto logoff
a user after a certain period of idle time; however, this
appears only effective for the user configuring the task
(i.e., Administrator), and doesn't affect other users
logging into the same computer.

As an administrator of over 200 XP Pro computers and
several hundred students who utilize them, I would like to
know if there is a way to make this universal for all
computers/students without spending months configuring each
system? My reasoning is that sometimes students will lock
out a teaching lab computer while taking a break, going to
lunch, etc. and this is quite annoying to other students
who need to use them.

Any advice would be greatly appreciated.