I'll side with Kazan on this one. You'll need to update your GART driver, which is usually done by updating your motherboard chipset drivers. In my 9800 instruction manual, this is a big reason why cards wont display in 2K/XP upon installing the card. What I'd do in order to get the card to work correctly is:
1- download the newest chipset drivers for your motherboard.
2- grab Driver Cleaner 3 from
driverheaven.net 3- Download the latest drivers for your videocard, the Cat's probably, or a good alternative are the Omega drivers from
omegadrivers.netUpdate your chipset drivers, which in doing so, should drop an updated AGP GART in your system. This will allow Windows to talk to your card properly, albeit in very ugly colors and resolutions without proper drivers. At least you can see though. After you update the chipset, try running the nvidia uninstall to uninstall the drivers. then use driver cleaner 3 following it's instructions to the letter. then you should be able to shut down the PC, stick the new card in, power on the PC and boot to windows. If this doesnt work, you'll probably have to reformat and install 2K fresh again, along with a chipset update.
Then install the drivers from ATI when windows loads up, and you should be rockin'. Just remember to hit CANCEL whenever Windows finds a display adapter and display controller. Cancel those and just run the ATI install program. That'll drop the correct files in the places they need to be.