If the outage was preceded by a power surge, which they often are, it can damage your system even if it's turned off. If you had a surge protector on it, and you've verified that is still ok (most just blow their fuse at the first major surge and are then useless) then you might be able to get it to come back up with just a cmos reset, if there's no permanent damage. This is a simple procedure, but finding the right jumper can be difficult if you don't know what you're looking for. Search around, if you can find a motherboard manual or specific instructions online I'd give that a go.

Since moving to Seattle I've lost a graphics card and two power supplies to dirty power... invested in an uninterruptable power supply (UPS) and haven't had a problem since.