make sure you have all the correct power connections connected to the card and that your power supply can handle to load. The reason why xp wont see the graphix card when connected through integrated is because bios automatically disables any agp.
1. take out graphics card
2. restart pc and in bios during post ( del usually )
3. make sure you select the agp setting or disable onboard , save and turn off.
4. put graphics card in reboot and it should turn on.
5. uninstall prev drivers even if same driver is used, restart and download/install driver through amd.
6. restart and your good to go!
that graphics card isn't agp its pcie which means it will 0% work with agp port. will need a agp card or a new mb.