Finding & Installing Default VGA Driver w/Windows XP

I having a hard time installing my ATI Mobility Radeon 9000 video drivers on my Dell Latitude D600, which is running Windows XP Professional.

I've got the most recent driver, but when I go to install it, I get a INF error, that says, "video driver not found". A subsequent dialog box suggests installing the default VGA driver for my laptop monitor. I assume this is suggested so that the ATI video driver upgrade will be able to find an INF the next time around, and be able to install itself.

I'm familiar with Windows, but new to Windows XP. Where do I direct the system to look for the default VGA drivers? Under Win98, those files were under the System folder and if you designated the default video display driver, it would find the necessary driver files easily enough.

Anybody able to give me a hint, clue or direction that will take some of the "randomness" out of what I'll probably end up doing tonight?