Actually had a tech guy come out and test it. We swapped out the video cards and ram 'n everything. He says it's definitely the motherboard, so I'm trying to find the exact same one so Windows doesn't have to be reinstalled (though Choj tells me not all motherboards would require that Windows be reinstalled anyway). I called all the local "mom 'n pop" shops, but none of them had the motherboard.
This online place does though:
http://www.pcprogress.com/product.asp?PID=ABAS8
So I might end up doing that. Gonna talk to the tech guy first and see what he thinks