follow an unistall routine , and use driver cleaner its the best way . here are the instructions from driver cleaner i never do #1, 6,or 7 thou
ATI:
1. Unplug nic card or modem from net or disconnect
2. Remove ATI driver from add/remove programs then remove the control panel from add/remove programs
3. Reboot into safe mode (F8 during boot up)
4. On reboot into safe mode WinXP SP1/SP2 will auto detect and install drivers. Just let it do its thing. If you can cancel out of the auto install hardware wizard then skip the rest and run Driver Cleaner! If you can NOT cancel out of auto detect wizard then...
5. Navigate to device manager->display adapter->uninstall and/or remove ATI display adapter but do not reboot
6. Disable any AntiVirus Software (If you don't disable is than it could give trouble)
7. Run Cab Cleaner (not needed, but recommended)
8. Run Driver Cleaner
9. Empty recycle bin and reboot
10. Install the new drivers and control panel