|So there is a couple possibilities... but first of all, did you have the PC plugged into a "good" power strip? with Surge protection? If not, then you should, but it's too late now.|
If its a system you are just building, I would recommend replacing the Motherboard. You should be able to return it wihin "x" days and be able to exchange it.
Its possible that it's your power supply, but probably not likely.