|How about backing up a bit & explain WHY you need to install the driver? What driver are you using now?|
Go to Device Manager & click the "+" next to Display adapters...what's listed? Right click on it, click Properties, then click on the Driver tab...what's listed for Provider, Date & Version?
And how is ATI telling you that the driver on the disc is the wrong driver? Maybe you need to install the ATI chipset driver as well?
I suggest you use the link provided by DAVEINCAPS, change the OS to WinXP, then download & install the video driver (last on the list).