I'm typing this from my work computer.
My Sony Vaio tower at home refuses to power up. When I hit the power button, I get power for about a 1/2 a second & then it just goes dead. I've opened up the tower & cleaned it all up, in addition to checking all the connections. A green light on one of the boards still glows when the power cord is connected. Another piece of info that may be of interest is that when my computer was functioning, it never hibernated (even though I had it set up to hibernate after 20 min. of no use).
Any ideas, guys?
I believe power supplies have 2 sections to them. One supplies a small amount of power to the board and the other supplies the rest of the power to actually run the computer. The reason I say this is my roommate recently built himself a computer and got a bad, but new power supply. It gave enough juice to light up some of the small LEDs on the board, but wouldn't actually come on to boot up the computer.
So, my guess is it's your power supply. They will fail...eventually. My old computer, when I put it into hibernation, the power supply still runs like it's not in hibernation. The new computer I built from scratch has a new power supply in it. When I put it in hibernation it goes off completely. Absolultely nothing is on, but will start right up when I move the mouse.
Is your power supply old? What wattage is it? You can buy a 500W supply, which should be more than plenty, for pretty cheap. Try newegg.com. I never liked them before when they were the new kids on the block, but now they've got the best prices, very reliable and good customer service. I bought everything for my new build from them. BTW, my power supply is a 550W BFG Technologies.