It matters whether this is XP Pro or Home.
If either, and the filestore is NTFS, setting registry control on the control panel applet will work. (If XP Home, you need to logon as Administator in Safe Mode).
While it can be worked around with the RUN service, or through the Control Panel, linney, myself and others have written a fairly comprehensive guide to killing user access to date/time in the XP forum.
Do a keyword search on "date" and click the button to search "subject lines".
If you apply all the security measure suggested in the links yo will discover, nobody but the Administrator will be able to set the date/time.
I should note that in the more benign cases of the fixes, it seemingly appears that a change is possible. But it is not persistent between logons. In the more extreme cases no change would be possible, even with XP Home.