Rose is still sacked out makin' z's, but I think her idea was that if the power supply was disconnected from the motherboard and all the drives, plugged into the wall outlet, and still didn't power up when you flipped the switch, then the power supply was probably at fault. The fan at least should come on...
Do you have another power supply you can swap with, to see if the problem follows the suspect supply?
I don't have another power supply, I'm leery of them. I do know where there's a techie store in town so I'll haul the computer over there today or tomorrow and see what they can do for me.