So yesterday I did a clean install of Mountain Lion, and everything worked out fine. I rebooted a few times, no problems. Then today the battery ran out while I was away, and now the computer can't boot - as soon as I plug in the power cable, the indicator light on the front lights up and I hear the hard drive spin up (all this without pushing the power button). Then it suddenly stops after a second, and repeats the same loop again and again - the screen remains black the whole time. I tried taking out the hard drive and plugging it into another computer via USB, and it looks fine. However, when it's back in my computer, the problem continues. Does anyone have any clue what this could be? I figure it's the motherboard or power supply since the hard drive seems fine. Any ideas on what I can do next?