ATX box won't power up

[jobert]

A friend for whom I built an ATX machine says it won't power up after being unplugged for a week. (It's worked fine for two years.) I can't remember the troubleshooting sequence for this, but I think it's simple. They live on Nantucket Island... I don't think I want to make an onsite service call! Anyone help?

 

[SocrPlyr]

first ask if when the press the power button they hear anything at all.
then if they don't if you trust them have them open it up and make sure the atx power cable is plugged in securely to the motherboard and check all cables like the external power cable etc.
then if that doesn't work unplug it from the wall and hold the power button for about 5-10 seconds. then plug it back in and try again.
if none of that works the power supply may be dead.
(all of this assuming that they hear absolutely nothing when they hit the power button)
if they do hear something it could be something totally different like agp card not in right or some other bad cable etc.