1)Get the "Display Driver" from here:
http://ati.amd.com/support/drivers/xp/radeonx-xp.html
2)Try to install the driver. You will get a "No compatible device found" error.
3)Go to the "Add Hardware" wizard in the Control Panel.
4)Choose to install with the "Have Disk" option.
5)Use the browse function to find the place where you originally extracted the setup files and choose the .inf.
6)Select Radeon X1200, choose install anyways and voila!