It sounds as though I'm having the same problem (or a very similar one) as dmdmkm on a PC I'm working on. I've worked on computers for years and this is the first time I have come across this problem. I was brought an eMachines T2341 (2300+ AMD Athlon w/ 250W power supply) that would no longer boot when the power button was pressed. My first guess was that either the power supply was dead, the power switch on the tower was broken, or the motherboard was fried. To kill two birds with one stone, I bought a new tower with a 350W power supply and transferred all the components over to it. Now when I go to boot the PC, it powers up for 1-2 seconds and then shuts right off. The only things plugged into this motherboard are a PCI modem and a stick of memory (128MB DDR PC 2100); everything else is built into the motherboard. If anyone has a suggestion that can help me either fix this problem or narrow the problem down so that I can identify exactly what's wrong with the PC (so I won't have to go though all of this again if it ever shows up in a future PC); it would be greatly appreciated. Thank you.