Why not just enable password protection on your accounts, and set the screensaver to use password protection as well (assuming this is Win2000 or WinXP)? That'll keep other users on a short leash, yes Precious :evil: You can leave a non-password-protected Limited-class account for others to use, if you don't want them formatting hard drives. A Limited account (or "Restricted-User" account in Win2000) does not have the power to format hard drives.
This strategy could save you a lot more headaches than just formatting of drives 🙂 Spyware and adware (or other software you might not want) cannot be installed using a Limited/Restricted account. If the computer is thoroughly subverted then this may not hold true, I've seen at least one spyware that once it's in, it arranges so that even Restricted Users can reinstall it. But if you get it properly locked down from the start, then you hold the keys.