I've just installed an EVGA 8800GT card, replacing my EVGA 7900gs.
When my computer restarted Windows (Vista x32 Home Premium) found an unknown device. I installed the drivers from the CD enclosed with the card. After install and a restart, windows reported an unknown device. It tried to auto-install drivers and failed, recognizing the device as a storage device.
I haven't encountered this before, but I would double-check the BIOS to make sure you have integrated graphics disabled. Also I've read it's important to uninstall drivers from your previous graphic card before installing drivers for a new one.
This would be my sequence of events:
1. Check BIOS - disable integrated graphics
2. Boot up and see if you have the same problem as before
IF THE PROBLEM CONTINUES...
3. Uninstall old 7900GS drivers and Reboot
4. Install new 8800GT drivers and Reboot
Thanks for the advice
My board does not have integrated graphics and I uninstalled before switching graphics cards, but it's always worth
trying again. I may download a driver cleaner if I can find a reputable one and try that as well after uninstalling the drivers again.