You would need to provide more information, although I probably couldn't help you if you did.
But I'm installing Debian 3.0r2 as well and using an ATI 9800 pro. The drivers that ATI provides are packaged as an RPM, and they didn't seem to help much. One thing you can do is to stick a Knoppix CD in and look at the way it configures your system, then use that information to configure Debian.