I have 3 Pc's in my business building where we recently had a new roof put on. This week, I've been checking our pc's (72) to make sure everything is still working. I've found 3 in which I can use the VGA ports for video display, but not the DVI ports. I've ruled out the monitors, the cables, and the video cards themselves. These pc's use the Windows XP Pro operating system. Also, before our christmas vacation, there were no problems that were reported to me, except for one of the digitaless pc's in which I replaced the motherboard. Does anyone have any ideas?