Unless you plan to use it mostly under windows, my first recommendation would be to return the card and pick up an equivalent Nvidia model (FX 5900XT). Frankly, Nvidia's linux drivers are so much better than ATI's that it's not funny.
And I own a Radeon 9600XT myself, and use it under linux. Believe me, you could do without my trouble.
However, if you're stuck with the radeon, I'd suggest a trip over to the linux forum at rage3d.com, where there are some excellent tutorials on making linux and ati play ball nicely.