We went on a short, 2 day, vacation and my wife unplugged her computer since we live in the LIGHTENING capital of the world. Upon our return she plugged in the computer and pressed the button. Nothing happened. No fans, no boot. I opened the computer and a greeen LED on the motherboard lights when I apply power to the computer. It is a EMachines about 1 1/2 years old running XP. Could the battery cause this problem? If so, what do I need to do to correct it.Sounds like you're power supply is about dead. How many watts is it? It should say... All you need to do is go buy another one from a computer store with the same wattage, and replace it.

FlameThe power supply wattage is 250W. I had a spare 100W supply byt the P8 plug was different so I couldn't even attempt it. What about the plug array? Shouldn't I be concerned about P8 which plugs into the motherboard?You might want to TRY reseating the RAM.Reseated RAM........No change.
The battery is not the issue, but the power supply may be. You will need to get an appropriate replacement. Check witth eMachines to see if this is some sort of proprietary unit, or try with a known working one of SUFFICIENT wattage and plug type.If I have a 250W power supply, can I go larger? Say, 300W. I went to Newegg and they have them there and the plug arragement looks the same as the one I have. Any suggestions on a brand that you have had good results with? The one that I have is Bestec.EMachines website indicates that I should change the cooling fan for the processor when I change the power supply. Sound right?Probably correct, especially if they recommend it. 350 w is probably the minimum to look at. Antec or Thermaltake are good brands. Usually with PSU's you get what you pay for. The Bestec was dirt cheap. That's why they used it. Some manufacturer's, like Dell, have proprietary power supplies. That's why I ASKED. At least Newegg has a good RMA policy if it doesn't work. I received and changed the power supply and cpu fan. STILL no thing happens when I press the button. Any other ideas?