This is what I did when I switched from a GF2 Ultra to a ATI 9700 Pro on WinXP. Uninstall the GF2, remove every Reg Key containing nVidia> shut down. Replace card and boot to generic Disp Drivers and not install Radeon drivers yet. Update to DX9 and reboot (very imp). Then, now install Catalist 3.1 (Radeon Drivers) and control panel.
Went smooth and now running an ATI OEM at 365/330.
Stout