I am having similar issue. Prior to getting ATI AIW 9800 Pro, I had
Asus GeForce 4 (AGP) + Matrox Millenium (PCI). These worked well
together. After replacing GeForce card with ATI, ATI drivers would not
install - it simply hangs (and have to push Reset button on my
machine)!
I tried all those BIOS settings suggested by ATI Support Rep - 'canned
response', and reinstalling Operating system! I gave up, and took that
Matrox card out and installed drivers and accompanying software.
After installing drivers, I put that pci card back, and on startup, I
get an error message from ATI Control Panel (one of those XP message
asking if I wanted to report the error). Experience with ATI had been
positive one until now

Did Anyone out there get multiple video
cards working?
I have: ASUS M/B - VIA KT333 Chipset (with latest AGP Drivers from
viaarena.com), Athlon 1800+, 1G PC2700 DDR, ATI AIW 9800 Pro (AGP),
Matrox Millenium (4M PCI), Sound Blaster Live Value!
Thanks
Gabe
"D.Currie" <(E-Mail Removed)> wrote in message news:<c11jpt$1diokb$(E-Mail Removed)>...
> Some cards won't function as a secondary card, they will only work as the
> primary. You can try changing the setting in the bios to boot from the PCI
> and see if both will work that way. If not, you'll need to get a different
> card to use as secondary; just make sure that it will function that way.
>