There is a great commercial product called DeepFreeze from faronics.com.
My NGO uses DeepFreeze on all Windows installations in Africa & Asia, where malware is ubiquitous. So far, none of our PCs have been successfully hacked, because whenever a virus or other infection is suspected, rebooting puts the PC back to its original clean state. Anything that had been changed, including web caches, cookies, screensavers, usage history... every change since the original setup, is erased. This type of software is perfect for cybercafe setups like the ACs and FLs.... it's inexpensive too.

Microsoft had a free product called SteadyState, which was pretty good, but they just dropped support for it.