Try to boot up again. If still no response, the first places to check would be power supply and motherboard. Even though the LED lights, there could still be one of the power leads not powering on. If you have access to another power supply or tester, I would start there. Then if that is OK, and no other items are plugged in, try the motherboard by itself. Of course it cannot proceed with nothing in it, but then if your are successful, start adding hardware until it fails or try a new or known working video card and install that so you can see what the BIOS says. Then try adding hardware one at a time until you get a failure. It would be much easier to try your hardware one at a time in a working system, if you can get someone to agree to that, however. Of course you stand the chance of taking out the other working system with that approach.