How can I stop some one from changing the clock on my computer? Is there any way of locking selected functions

you can lock it down using the group policy editor.

use at your own risk, wont guide you around through there cuz you can really screw yourself up

start > run > gpedit.msc

look around through there and becareful what you play with =)

I hate to give that as an answer to anything, but it's true in this case. Everything you do on your system depends on the clock. When a file is written or updated, it uses the clock to set the modification time of the file. Any program that involves any kind of delay uses the clock. This includes Web browsing. The system logging uses the clock. The services use the clock.

What is the reason that you want it stopped? there could be alternatives?

yeah you can try using Group Policy Editor

and also limiting functions with User Account Settings

Set an administrative password, and set up an activity monitor, find out who it is and tell them to quit it.

CREATE AN ADMINISTRATOR ACCOUNT WITH PASWORD AND A GUEST ACCOUNT AND LET OTHERS TO LOGIN FROM THE GUEST ACCOUNT