computer powers itself off after 1 second

I saw this question recently, but did not pay attention at the time, and now I can't find it. Anyway, I borrowed my cpu out of an up and running computer to update the bios on a new board for a differnt computer so that it would handle a pentium d and that worked fine. When I replaced the cpu and fan and powered it up, the fan did about 1 revolution and then it all shut down. I tried a different power supply and it was the same. I have tested both supplies with my tester and discovered that if I don't have the 4 pin 12v plugged in to the mother board the cpu fan comes on and stays on, still no post of course.. I have reset the cmos with the jumper and that changed nothing. I have taken out all but 1 stick of memory. My computer (bare bones at the moment).

asus p5ad2 premium
Zalman 9500 cpu fan
3.2 ghz prescott
seasonic s12 380w psu
256m kingston memory (usually 1gb)
asus video card(don't remember #)
Thanks!