New motherboard

My 875p motherboard went out. I was moving and sometime took the screws out. Powered it up. Motherboard didn't have a ground so it got fried. Anyway, I replaced it since with another 875p. Problem is, now, when I try to boot it up. I will stay on for about 15-20 seconds and power itself back down. It stays up long enough to check the processor out. So I dont think its a problem. All the jumpers are correct. So now I am at my wits end. Can anyone help?