http://www.pcpower.com/support/ATX_troubleshoot.htm has a very simple test to perform to see if the power supply is working. If it passes this test, the power supply may still be bad (I know from personal experience), but if it fails the test, then you know the power supply is bad, not necessarily the motherboard. The test simulates the signal that the motherboard sends to the power supply to start up, and it requires a hard drive load to work. ("hard drive load" means that the power supply must be connected to at least one hard drive for the test to work.) Unfortunately, the problems that you are experiencing are difficult to pin down without swapping parts. The issue is that the problem may be located in the power supply, the hard drive, or the motherboard. I am not sure if the green light lighting up is an indicator of a good power supply or not. An ATX power supply needs a load on it (such as a hard drive) to start up, but it may have a separate circuit that works to power the green light. I, myself, purchased a relatively cheap power supply ($30) from CompUSA the last time I had this problem on my wife's computer. Her computer passed the test above, but did not start. When I swapped out my power supply with hers, it then started. So, I used the cheap power supply until I could get a new, good one from PC Power and Cooling. Now I have a spare, and, should the problem arise again, I can easily swap out the power supply. I have had a relatively new power supply (a cheap one that came with the case) fail on a new build for a friend after about six months, so I think that cheap power supplies ARE the weakest link. Even my two power supplies from PCP&C failed after about seven years. (Antec makes a well respected power supply for much less money, but, in my opinion and that of some of the other moderators here, PCP&C is the premium brand.) Another thing that you could check is the power button. Just short out the two connectors on the power switch, and, if the computer starts, then you know that it is the switch! It is not an on/off switch - it just sends a quick burst of power to the mb to tell it to start up. The test above should pass in that case. If the power switch is not accessible, you can short out the pins on the motherboard where the power wires connect, but that might be a bit tricky. If you are not afraid of getting shocked badly, you can open the case on the power supply (with the cord unplugged, of course!!!) and look to see if anything looks burned or scorched. The power supply on my friend's computer had a badly scorched part. Even if the power supply is unplugged, it is still dangerous to open the case, because there are capacitors in there that store a great deal of charge, so you must NOT touch anything inside!!! BE CAREFUL!!! HTH, Dean Kukral CC: [log in to unmask] ----- Original Message ----- From: "Joe Rydzy" <[log in to unmask]> To: <[log in to unmask]> Sent: Sunday, August 26, 2007 4:38 PM Subject: [PCBUILD] Computer won't start Ok, my friend has an e-machine and has been working fine for 3 years. All of the sudden when you press the button to start the computer nothing happens like it doesn't have power. Checked incoming power and 120 is going to the computer and opened up the case and you can see a green light on the computer board which one would think that the power supply is working. So any ideas why it won't turn on? Could not find any fuse anywhere or any reset button. thanks, Joe Rydzy PCBUILD's List Owners: Bob Wright<[log in to unmask]> Drew Dunn<[log in to unmask]>