I have just built a new quad core computer. But it wont boot. I have a 500w PSU (Thermaltake 500 NP) and I have the voltage set to 115, I have a lot of stuff in the case, should I have it set to 230? It is a power issue, and I know that it is not the PSU because I have tested it in another computer, works fine.

If the line voltage at the wall outlet is 115/120v, the PSU should be set to 115v. Did you benchtest the motherboard/CPU/RAM to confirm it works BEFORE installing it in the case? If not, you might wanna consider gutting the case & starting from scratch. "And that's the fishing line, because Sharkboy said so!"

Well, the thing wont even turn on, like, nothing will happen, not even a fan will turn. I know that the board is not doa, because if I put the HDD led head connector in the wrong way, it will stay on (in the front of the case).

You're not understanding. If you didn't benchtest, you have no idea if the board works. However, if you HAD benched it & confirmed it was working, THEN installed it in the case & it didn't work, you would know that something went wrong with the installation...such as having a standoff in the wrong place. Right now, you're just spinning your wheels. See responses # 1,2,3: http://www.computing.net/answers/ha... "And that's the fishing line, because Sharkboy said so!"

Follow Jam's advice!!!

Got it to work!!! Thanks!!! It turns on when the mobo is outside the case.

Now that you have bench-tested it outside the case successfully, have you tried mounting it inside the case again? If so, is it working OK? If not, you probably have something that is shorting the system out (e.g., misplaced motherboard standoff, as jam suggested, or a wire hitting where it shouldn't). 1 Corinthians 15:3-4