Rage Pro cards were not supported in 10.5.8 so you can copy the ATIRage .kexts from /System/Library/Extensions of a 10.4.11 drive to your new one. It will update the kext cache and then reboot. You will no longer have no extension loaded in the system profiler for your video card. I'm not sure what benefit this has but I still can't play Wolfenstein because it won't load OpenGL. This works fine in 10.4.11.

[crarko adds: I admit to having a weakness for the G3/G4 towers. I loved my Blue and White G3. Anything which prolongs their life is a good tip.]