I bet the harddrive is the problem but it could also be the power supply. From the sounds of it, some of the other people on this forum know quite a bit more about this than me, but if I were you I'd unplug all the hard drives and see if it even gets to the set up screen. If it can't then you know your hard drives are probably not the problem. If you have an extra powersupply or can get your hands on someone elses I would swap it into your machine and see if that helps. I had a power supply go out on me and it made my computer act crazy for a while while it slowly died more and more. I also once had a hard drive die on me. It made a clicking noise that quickly became a grinding sound. I hadn't backed up my thesis in a few week and I nearly shat myself. Lucky for me I was quick on the draw with my USB drive and everything turned out OK. Good Luck dude.