My family often inadvertently leaves our home computers on overnight. This used to annoy me, but not any more.
Timed Shutdown can be used to automatically shutdown a PC. It supports shutdown, reboot and logoff at a user-specified time, after a countdown has elapsed, when the CPU usage reaches a certain level or when your Internet connection is disconnected. The program sits in the system tray when running so it can be easily aborted. It can optionally display a warning message before taking action. Timed Shutdown can also be run from the command line.