I posted this as a reply to a couple of people who reported eMachine problems similar to mine. What I'm looking for is: using a voltmeter, does anybody know what each pin should read and a "proper" technique for SAFELY testing a Power Supply, ATX w/4-Pin aux connector.

I have an interesting problem like this...I'm not sure how to repair it yet, but I have found a temporary solution: Unplug the small, 4-wire connector that comes from the Power Supply from the logic board. Turn on the machine and let it run for 15 secs or so. Now, you HAVE to unplug the AC cord from the Power Supply...pressing the button seems to have no effect, no matter HOW long I hold it. I reconnect the wire and VOILA! the thing boots like there's no problem. There is no BIOS update available (as of 2008-Jun) and the only card in the machine is the modem that it came with, so I'm gonna replace the CHEAP 120w PS with a beefy one and see if it's the PS.