Machine Not Powering Up

Okay, 

I gave my rig to my mate for a few months (I wasn't using it), I get it back today and the thing isn't powering up. 

I know the power supply is receiving power and providing it to the motherboard because one of the LEDs on the motherboard is on. My next suspicion was that the line between the power button and the motherboard became damaged disconnected but it does seem secure. 

Any suggestions on the next course of action. 

Thanks, 

Dev. 

Any beeps at all, or just nada when you press the power button?

Do the fans even spin up?  If not, I'd check the PSU and power switch first...

No fans, no beeps. Almost as if I hadn't plugged it in. My initial suspicion was that the PSU had given way. However I noticed one of the LEDs on the motherboard was on, this indicates that at least the PSU is receiving power and giving it to the motherboard and that the motherboard was also receiving it. My next step was to check the connection between the power button and the motherboard but it does seem secure. Somtimes these can come loose with banging doors and rough smacking of the button. Not something I would do but it was at my mates house.

I'm thinking maybe I could short the power button on the system panel at the bottom right of the motherboard. At least this would confirm if it was the power button or not.

Anyone have any suggestion on how to do this? If I were to guess I would say the intake needs +5v dc.

Re-seat all the PS connections to the motherboard.  If the symptoms persist, I'd try:

1. Connecting/trying a different power switch (if you have an old case handy).
2. Disconnect all the drives, remove every card, and unplug the RAM.  Try it and see if it will give you beeps indicating lack of RAM/video.  If it starts coming to life, plug everything back in one-step/reboot at a time to find the culprit.
3. If it's still not giving you any beeps, either the motherboard's bad or the PS is (if the motherboard does not have a loose screw wedged somewhere.  ).  You should get some beeps even if the CPU's bad.

I'm thinking along the same lines as you either motherboard or PSU. If it was any other component I could expect beeps but nada. I'll follow those steps in a bit. Quite busy at the moment with college. Will check back in a few days with an update.