I made this small app to try and lock a computer in Media Center until a password is entered.

What it does:

1. Saves encrypted password to "key.sl" file (saves to location of MC_Lock.exe)
2. Runs Media Center
3. Keeps Media Center on top & active
4. Locks mouse within Media Center window
5. Closes taskmanager if detected
6. Locks screen & asks for password if Media Center is closed
7. Restarts Media Center if password isn't entered

Other info:

•  You can still use Alt+Enter to restore/fullscreen Media Center
•  Alt+F4 will close Media Center and prompt for a password
•  Apps that don't actually run within Media Center won't display (ex. Solitaire)
• This probably won't let HD-DVDs or Blu-ray disks play properly, though I haven't tested this.

This is still a beta, so there might be some bugs - let me know what you guys think.

Download it from the Apps page.