Faronics Deep Freeze is an amazing piece of software that will allow you to literally freeze your operating environment in place so that nothing is written over without your consent.
Deep Freeze works by creating a virtual state of your computer and keeps malicious content from ruining your Operating System and programs, yet does so without restricting user access. As it has saved my can many a time, I would recommend Faronics Deep Freeze for anyone who wishes their operating system would stay as fresh as the day it was installed.