I had XP Pro running with dual monitors for a couple of years, switched out monitors from time to time and no problem. I've got an Intel 2.8 MB with onboard video connected to one monitor, and an ATI Rage Pro to the other monitor. Worked great till I had to replace the hard drive and reinstall XP Pro. I'm running SP3 with all updates. Now what happens is, whichever video adapter I make primary in the BIOS, XP comes up on it, with the drivers okay, and the non-primary one XP detects but Device Manager says the driver isn't installed. And nothing I can do will make it accept the driver for the non- primary one. But if I reboot and change the primary video adapter, then it comes up with the other adapter & monitor just great and the FIRST one is now failing to start. When I go to Settings on Display Properties, I only see one monitor in either case. I've tried taking out the ATI and starting without it, then and putting it back and restarting, no change. I don't know why this install of XP will only accept the primary video adapter and not a second one.