Just upgraded my computer to a new motherboard. Whenever I try to turn it on the fans power on for a second then shut off. I have checked all connections, reseated the ram, and everything else I could think of. The motherboard is a gigabyte ga-g31m-es2l.
My initial thoughts are CPU Cooler not seated correctly Thermal paste wasn't re-applied PSU faulty But I can't say for sure Check the CPU Cooler is seated properly. If it wasn't, and the CPU was overheating, it will most likely shut down the system (although mine didn't - it just started smelling of burning ). If there isn't sufficient thermal paste between the CPU and cooler, then the cooler might not work well, and once again it would overheat. I don't think this is likely to be the case, but you never know. Finally the PSU might not be able to cope with the new motherboard. I don't know a lot about PSU's, but it's a guess
is the motherboard touching the back of the case at all? (short circuitin) have you got it sat right on top of the spacers? are you using after market cpu heatsink? if you are and have a metal base plate make sure it isn't touchin any soldering on the backof the motherboard, if it is apply some insulation tape over it. If no luck with that, try building it outside of the case on a piece of cardboard or somethin. If no luck with that I would most likely say its PSU.
i strongly agree with thomas, check the cpu heatsink, I'd remove all unnecessary hardware, including ram and dvd drives, hdds, etc and retry. if it does not shut down then it has to be one of the devices