when sober, try clearing the cmos, and take out any cards you don't need, such as soundcards. If you have more than one stick of ram, try booting with just one stick and maybe try a different memory slot. The cpu may be fine, could be psu related, or simply the bios had a hissy and a clearing the cmos will sort it.
Basically, set the pc up with the bare minimum hardware it needs to work and double check everything is seated properly, especially the power connectors, memory and graphics card. I've had pcs look dead as door knockers and all it took to fix em was taking the power connector out the mobo and reseating it again.
EDIT Ytareh beat me too it
