Some machines require the motherboard drivers first then the video card will appear.
I have a GeForce FX5500 graphics card on a ABIT AN7 mboard that worked perfectly before I had to run Repair on XP (with all updates)for another problem. For some reason the repair installed a XP generic VGA driver. The graphics card does not show up in Device Manager and in Display Properties under Adapter it shows non plug and play with a generic driver. I have tried to update the driver but when I get to Have Disk I point it to the correct .inf file and nothing happens. If I try to install the driver from the correct Navidia setup file I get a message that the hardware for this device is not compatable with navidia software. It seems that XP does not see the card however if I run a little system analyser program the card shows up just fine. I even tried swapping out this card with a GF4t 4200 (a little slower card) and no change XP dose not see it eather. I have tried both the origional drivers on the CD and the latest from Navidia.