When I turn it on all the fans come on, the keyboard lights up momentarily and the CD lights up as the first boot device. But then nothing else happens. When it was working, the next thing that would happen is the keyboard would light up again and the monitor would come on. This no longer happens. I already changed the power supply and even tried removing one stick of memory at a time to eliminate a bad memory problem. The SATA hard drive is spinning so it maybe O.K. Since the bootup sequence doesn't get past checking the CD drive I suspect the Motherboard is not communicating with the hard drive.