Fix my Mobo?

I have a MSI Mobo with a Celeron processor.
almost like this one http://images.google.com/imgres?imgurl=http://images.tigerdirect.com/itemDetails/M452-2652/M452-2652-out2-hl.jpg&imgrefurl=http://www.tigerdirect.com/applications/SearchTools/item-Details.asp%3FEdpNo%3D2366188%26sku%3DM452-2652&h=418&w=430&sz=168&hl=en&start=3&um=1&tbnid=YvAgj47h6JAnDM:&tbnh=122&tbnw=126&prev=/images%3Fq%3Dmsi%2Bmobo%26svnum%3D10%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DG
(I hope this link works)
I striped it down to the bare mobo and power supply (known working processor ram and ps)
So this is what happens…when i have the atx 12v connector in the fan comes on but no screen but if i plug it in then try to cut it on the fan hesatates then nothing happens
Its a couple years old and im trying to fix it.