I have a computer that is about a year old. I had it built so don't know much about its guts. One morning about a week ago it shut it's self down. I thought it was kind of strange but it rebooted no problem. A couple hours later it did it again. I rebooted again no problem. Before I left the room it shut down and won't reboot. It made a couple of buzzing noises but then wouldn't even do that. I replaced the Mother Board and still no luck. Have tried changing out the Power Supply with a known good one. Replaced the Processor, Checked the Hard Drives. All seem to work in other computers but the hard drives won't let me install on them in the other machine. (No operating system on the most important.) it seems like the main boot sector on the hard drive was wiped out as well. When I try to install nothing happens. The cpu just sits there. Any suggestions are very appreciated.