http://www.microsoft.com/windows/products/winfamily/sharedaccess/default.mspx
Keep your shared access computers running smoothly with Windows SteadyState
Upgrade today! Windows SteadyState Version 2.5 is now available with Windows Vista Support
Get SteadyState now
Are you ready to download Windows SteadyState for your genuine Windows XP or Windows Vista computer? There's no charge. Download it now, or look around and learn more.

See how easy it is to use
Not an IT professional? That's OK—it can be easy to manage shared computers that are hardened by Windows SteadyState for multiple users.
Lock down your user interface
Users sometimes go places and do things they shouldn't on shared machines. Now you can help protect sensitive locations and restrict user access to features such as Control Panel.

Ever wish you could undo everything?
You can't always prevent problems during a user session, but now you can undo the whole session. Learn how Windows SteadyState can return your computer and hard disk to its exact condition before the user touched it, simply by rebooting.
Troubleshooting
The Windows SteadyState overview FAQ may have the answers you need.
Learn more about Windows SteadyState