Shutting Down Windows
Have you ever tried to shut your computer down only to have it get stuck on the shut down screen?
Or maybe it's locked up beyond any help CTRL+ALT+DEL could give you. You may find that hitting the power button doesn't seem to do anything.
If you really need to force a shutdown via the power switch, press it in and hold for six seconds. That should turn the computer off.
But, take notice that you should only do this as a last resort. You should always try to shut your computer down properly.