Hmm, well it wasn't DOA then. I'm not sure about how good ECS is, but I suppose if they are really bad then the MB could be going bad already. Possibly flashing of the BIOS is necessary? Do you know if there's a new version out? Or the CPU could be having major overheating problems, and that could be why sometimes it boots up and sometimes it doesn't, and why it fails everytime it trys to do something relatively intensive, like a full screen video or game. Do you have the heatsink and fan properly installed? Do you have a heatsink that's suitable for your processor? Try getting an app or just checking the BIOS that shows your MB and CPU temperature. Or maybe the HDD's going. How new is the HDD?