HackyourWindows[dot]com

Prohibit access in Windows XP

This tutorial will show you how to deny access to people that have accounts on Windows, denying access to drives other than the C Drive that your operating system is on, folders, files, and programs. Note: Only the "Administrator" of Windows can do this, meaning the one who has full access of Windows and is also able to do system wide changes.

This is especially effective if you have a nosy kid and you don't want him to screw up your computers settings :)