Further to my earlier answer, these emachines along with the advent,medion,gaetway,packard bell, iqon, computers which come for the big shop in the high street all are based around the same motherboard buitl by trigem. All fail by blowing the capacitors on the motherboard around the processor socket. In most cases this causes the power supply to blow at the same time, but sometimes the pc will be attempt to boot but because the processor is at this point out of action, there is no boot display on the screen whilst everything else appears to be working. I have carried out the required motherboard replacement to these ranges of computers many times in the last 12 months with perfect results everytime. All but a few have also needed a power supply too.
Chrisf989, July 2008