Hello
tkillion20:
No you don't have to plug in Aux to power on an ATX power supply and system. Maybe the motherboard is dead. Who makes that motherboard by the way? I would try out a third ATX power supply to see what the result is.
Buycomp has Antec's great PP303X 300W POWER SUPPLY which is AMD recommended for Athlons for $37.82
http://www.us.buy.com/comp/product.asp?sku=10033276