If you're running XP Pro, click Start, Run and enter GPEDIT.MSC Go to:
Computer Configuration, Windows Settings, Security Settings, Local Policies,
User Rights Assignment. Look in the right pane for the Change the system
time. Modify this entry to take permissions away from the user Group in
question. You can assign individual Users here, as well.
GPEDIT.MSC does not exist in XP Home. In XP Home, you can accomplish this
by restricting access to the TIMEDATE.CPL file.
http://www.winguides.com/registry/display.php/969/
This can also be done on a per user basis, with the licensed version of the
Windows XP Security Console,
www.dougknox.com, Win XP Utilities section.
