I have junk AT PSU which only outputs:

5V cable: 4.84 V
-5V cable: -4.64 V
12V cable: 11.65 V
-12V cable: -11.17 V

however, the Power Good cable stays at GND, indicating that the voltage levels are not in spec, thus not letting the motherboard turn on. What did your other voltages look like? If they were as bad as mine, your MB shouldn't be powering up.

Side note: caps aren't bulging. Anyone know which components need replacing in this AT PSU (caps, regulator, inductor)?