You often hear about a pc not powering up.This could either be one of the following: 1.Mains power failure.2.Defective wiring. 3.Power supply faulty.4.Ram defective.5.Power not switched on ha!! ha!!! which i have found on many occasions.6.Now this an interesting one which i came upon in a computer magazine called pc format, which states that it could be because of static electricity.To rectify this you should unplug everything from the back of the case,hold the power button in for 30 seconds while the power is disconnected then plug it all back in.

Hope this is of use to somebody.
regards
v/man.