Help with a video card and dual monitor display

Hi,

I'm putting together a very old system for a disabled friend who can't
afford a modern PC, but I've run into a problem. He likes to play older
games like Half life, Unreal 1 etc, and can't afford the modern ones.
So what I've done is taken my old 350Mhz system which worked just fine
and bought a Savage4 Pro PCI video card and used it to replace the
Voodoo2 which worked fine but didn't offer high enough resolution to
play some games (Battle of Britain).

However, somehow I can't figure out how to disable the original video
adaptor (Sis 6326). I know the Savage4 is working because when I boot
into Win98 it recognises it but, here's the catch, it will only add it
as a SECOND display. I have to keep switching the monitor cable to the
second card just to test that DirectX etc is working on it.

I can't figure out a way around this. I've tried the BIOS (AMIBIOS) to
see if there's a way of disabling the onboard Sis 6326.. the closest I
can get is something about swapping AGP/PCI as main display... so I do
that and sure enough the second video card starts showing the bootup
screen, but then... the whole thing crashes in the middle of windows
bootup. Just freezes.

Can't figure out what's wrong. Could this be an IRQ conflict?

I just did something similar, and you are right about swapping AGP to
PCI in the Bios. After I did that I was able to boot using the new
card, but the computer would crash randomly. After doing some
investigating I went to my Hardware Device Manager and saw that there
was an exclamation mark on my old video card....so I went to it's
properties and disabled the driver and my computer hasn't crashed
since. The only other thing I can think of is that maybe the card is to
advanced for the older computer. Hope this helps.