Why won't it turn on? I have a HP desktop (DC7100c) and I turned it off last night and now it won't turn on. There is a green LED light on the motherboard that blinks approximately twice every second. I've tried jumping the PSU (Power Supply Unit) and the fan turned on.. Hmm.. So the Motherboard is on, blinking green, and the power supply works but I still can't get it to boot?? Why??? I'm COMFROOSED.

I've also tried to hold down that button in the inside with CMOS on the side of it but still, no luck.

I wish I had the money to get this fixed but sadly I don't. Hopefully someone can help me here. I also have Yahoo messenger (Phone call optional) if someone think they can help me with this problem.

Do you get any beeps when you switch it on?

No beeps, just a blicking LED light

The motherboard light should not be blinking. It should remain steady. I suggest you unplug and reconnect all components. If the issue is not resolved then it could be the power supply.

The green LED is connected to +5VSB. The light should be steady. If the load on +5VSB is too much, the green LED could go off, until the overload is removed. Occasionally, there is a functional problem with the power supply itself, and the flashing green is not a problem with the loading at all. So it could be a bad power supply.

The green LED on the motherboard, is connected directly to +5VSB, so monitors its every move. There should not be any logic devices in the way. If the LED flashes, that means the power supply is turning on and off, which is why that green LED is a very good indicator of how well the power supply is doing. The LED should never flash, and should be on steady and solid.

Take a look at the connectors on that 20/24 pin connector. Are they black/brown/melted/discoloured? If not, I suspect either a short or a bad PSU. I'd try taking the motherboard out, and setting it up on a non-static bag or cardboard box to see if that works to eliminate a short to your case. Failing that, i'd try and get a spare PSU from either another machine or a friend to swap in to see if it works. You may also change your mobo battery.