M Taylor,
Actually, before we go fully down the road of kiosk implementations, perhaps Faronics Deep Freeze will be sufficient for you.
Basically, you set the system up as you like it... then you "freeze" it. The theory goes that no matter what users do, or try to install, all you need to do is reboot and the system goes back to its frozen state.
You can "thaw" the machine for maintenance, your own personal use or whatever.