One way to check the power supply is to disconnect it from the MOBO and everything else. Then using a paper clip connect pin 14 of the MOBO power connector to one the black leads on the same connector. This will fool the power supply into staying on after you connect AC power. Then you can measure the voltages on all of the lines with a voltmeter and look for +12, -12, +5, -5, and 3.3 volts. Since there is no load on the power supply, some of the voltages may be off. If you find one, then connect a 100 ohm resistor between that lead and ground and check again. You can get one at Radioshack. If it is still off significantly (more than 10%), then the power supply may be bad.
