I have two graphics cards installed, and after my most recent re-format, only my main AGP is showing up. Setup:
Windows XP Pro
Radeon HD 3800 AGP (works)
Radeon 7200 PCI (does't work)
The PCI one just doesn't exist anywhere on my system... Tried various drivers and nothing works. When I try to install the drivers for it from ATI's website, it says it can't find any compatible hardware. Also, it does't show in my system information or Device Manager.
Any ideas? I'm going nuts here, I need my other 2 monitors for work!
You want it to work as a dumb extension device running on windows default VGA drivers and just update the HD3K.
Anywhoo, to the issue itself, assuming the R7200 worked to begin with (did you try it in other rigs?), could be a poorly seated card (try taking it out and put it back in, even in a different PCI slot).
Next possible issue, check mobo BIOS make sure no setting is preventing it from using PCI correctly. Posting system specs always helps people trouble shoot this stuff.
Next clean out the old drivers, shut down, remove the R7200, reboot clean system, update drivers, shut down, add R7200, reboot, and see if it is detected anew.