Default Screen Savers

I am looking for a way to make every use who logs into a computer to have thier screen saver set to the one I specify. I have a screen saver setup so that anytime the user is idle for more than 20 minutes it logs them off (on a Virtual PC running windows XP SP2 through VMRC) Any suggestions or if anyone can think of a better way let me know. Thanks.

 

Would it be acceptable to have the computer go into standby or hibernation? That is a system-wide setting and would be much easier.

 

Unfortunately, not an option. The issue here is lets say bob logs into the Virtual PC and then Drives to Mexico for the weekend. Steve logs in later and Bob is still on so Steve has to log bob off or use his account (in this case to do bad things). Now lets say Bob leaves for Mexico and his screen saver (which he can't change) is set for the special logoff screen saver. After 20 minutes of him not being there Steve will have to log in under his own name.

If someone knows a start up script or some PERL I could work with that would also be helpful so I can drop this whole screen saver thing and go for a more intelligent design