I recently put together a computer with parts purchased primarily from Newegg, but unfortunately, it won't turn on at all. I've got an ASRock P67 motherboard with an i5-2500k CPU powered by a Antec BP550.
When i had finished constructing it, I plugged it in, flipped the power switch, and attempted to power it up using the button on the motherboard itself. Nothing happened. I unplugged wires until I had power connected solely to the motherboard and video card, and nothing happened.
I had a friend remove the power supply from his computer and hook it up to mine (his is a 650W) and to my surprise, the computer turned on. It gave me the error that some parts were not connected (I hadn't yet connected the power to the hard drive, etc.) but after turning it off and turning it back on twice, it stopped working, in exactly the same fashion as before. He plugged his power back into his computer and it was fine. Obviously there's something in my computer that's not working, and as I'd prefer not to ship all of it back, I'd like to know if there's any way I can test each individual component.