Any shorted component can cause it not to power up. Remove everything from the mother board, if it has more then 1 memory stick remove all but 1. It should spin up the fans and at least stay running with just motherboard, 1 stick of memory and PS connected. If it still fails swap the memory stick with another one. If the fans still don't spin up it's most likely the motherboard. Electronics don't fair well from lack of use so it is even possible both PS are bad.
"Smart enough to know better, to old to care" ------ Dedicated Bat Cave Home Theater, JVC RS49U/Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 18TB DroboFS NAS