If your BIOS has that option you could access it typically by pressing F2 just keep an eye out for "Press X to enter setup" when he comp starts up.
Not every motherboard supports this feature though and it appears to be quite buggy. You may need a particular motherboard with particular jumper settings.
This proved quite insightful http://forums.whirlpool.net.au/archive/605498
Or you could just get a beefy UPS that puts the comp into low power when the power goes out. A typical outage would rarely go past the 8-12 hour mark.