Here's how you can manually install your Radeon 9500. If you have XP, just stick the card in without using the regular installation method found on the disk. Instead, after inserterting the card, go to the device manager, find the card under display adapters, and click "update driver". Then, you can search for that specific driver that is on the disk. After that, just update the drivers found on ATI's website.
That method has worked for me several times in problems such as that (damn Westell wirespeed sometimes has to be plugged into usb port when I'm missing my ethernet cable, and the installation disk is made for 98/ME).
I have a question of my own. I have Windows Update to automatically download on all 3 XP running comps. Is it normal to see a "New updates are ready to install" popup almost every day?
*edit*
Ewww Zxqv8, you ran a 9500 on a P3 500? What a waste. Reminds me of when I installed a 32 MB ATI All in Wonder on my PII 350... Some reason or another, the card overclocked itself, and I enjoy nice little lines running up and down the screen