This machine started locking up randomly and even during boot up - then quit booting at all. When powering on, I hear the hard drive activate and a fan like sound running, but nothing else including a blank screen. I noticed the cpu fan not running so I replaced that. The problem still existed. I suspected damage to the processor still thinking that it was a heat problem from the fan not running, so I replaced the cpu. Still same problem. My next step was the motherboard, which came with yet another cpu, but this didn't fix anything either. I know this shouldn't matter, but I had another harddrive so I went ahead and swaped that, too. Also, just wanting to rule out a bad monitor, I hooked it to a desktop monitor, but had the same blank screen. I'm at a loss for anything else to replace and check. Any help is appreciated.