A friend of mine said his computer did not even light up, so I told him I would take a look at it. Like he said, nothing happened when plugged in, no lights, no fan spinning etc, so I suspected the Power supply. I had an extra power supply laying around so I thought I would try it. I removed the older power supply and started to put in the newer power supply. I plugged the main harness into the motherboard, and then plugged it in. I then heard the fans start on both the power supply and on the CPU unit. I was convinced that it was the PS, and I had fixed the computer for him. I then connected all the other wires. Before putting the case cover back on, I plugged it in again. No fans spinning. I then removed all the harnesses except the one to the motherboard, still nothing. What happened ?? I can hear a very light hum coming from the PS when plugged in, but nothing else. Any suggestions as to what happened ?