Will M

I have an Acer M5100 desktop pc. AMD Phenom quad-core 2.2Ghz, 3 Gb of DDR2 ram, Nvidia 8800GT 512 MB video card. I properly shut down my pc last night, when I woke up it would not turn on. Nothing happens at all when I press the power button. After checking all connections on the motherboard, and trying each ram stick one at a time, I disconnected the power supply and used a paper clip in a 'U' shape in the green and adjacent black wire locations. The power supply fan itself turned on and was running(which didn't happen when everything was connected to the motherboard) but did it not power the one cooling fan that was the only thing connected to it. Would this suggest that the power supply is done? Or do you think I could be looking at a bigger, more expensive problem. Thanks in advance for your help!