@DeathByVisualStudio: Back when I was in highschool. My dad tried to limit the amount of time I and my brother spent on the computer by setting a password on the BIOS, so we wouldn't be able to use it if we were home before he returned for work.
He really should've picked a better password though, as both my brother and I were independently able to guess it within minutes (it was "ajax", his favourite football team). So much for the effectiveness of that measure.
The only downside was that whenever we'd hear the car arrive we'd have to drop whatever we were doing and turn it off, regardless of whether the game allowed you to save.