My BIOS is set so that I can press CTRL+F1 to turn on my computer, but I've only done that once or twice, because I leave my computer on all the time, as rbloedow and others do. I run Windows XP, and that OS, like Windows NT and 2000, is quite stable (capable of running 24/7 under a good load for several weeks and not needing a reboot). My guess is that the poster who has terrible instability problems (2 or 3 crashes each day) is using the outdated Windows 98 or ME, or [rare chance] has a serious hardware issue.
I can also sympathize with Davegod, because I had a keyboard with Power, Sleep, and Off buttons right underneath the Delete, End, and Page Down buttons (thus, right above the arrow keys). I can not count the number of times I accidentally turned off my computer via those damn piece of sh!t keys. Needless to say, I keep that keyboard in the closet, having replaced it a long time ago with a less annoying model.