Every process on a PC can be disabled, and sometimes the reason for doing it isn't obvious unless you are a System Administrator who has to do battle with meddlers...

My method for System Restore is to Ghost a backup of a hard drive at the point where it was working properly, then when someone mucks it up I can put it back to the point that I have chosen!

Their desktop settings, documents and email are on a fileserver, so they can't do too much damage... and System Restore can take up valuable disk space, as Cluin mentioned.

The only drawback with such a method is the plethora of updates from Micro$haft... so a Ghost is usually needed around every three months or so to keep on top of things.

Did you know you can use Disk Cleanup (right click on the hard drive icon in 'My Computer' and select Properties) to remove all but the most recent restore point? This relieves drive space, and is perfectly safe if your PC is behaving properly when you do it. I would recommend you do a restart immediately before you run Disk Cleanup, as this almost certainly ensures you have no issues...!