Graphics cards not starting

My wife's PC was working fine until recently when a hard disk (an IBM
Deathstar - what else?!) failed and I had to reinstall windows onto a
new hard disk.

It was working fine after the reinstall as well, though the
reinstallation didn't go at all smoothly, and the two graphics cards
(a PCI S3 Trio 32/64 and an AGP Nvidia GeForce4 MX 440) were playing
nicely together and running two screens.

And then after a few days, this stopped working. The monitor driven
by the AGP card didn't get a signal at all.

In the device drivers section, the AGP card has an exclamation mark
icon next to it and reports a "This device cannot start (Code 10)"
error.

Thinking the Nvidia card might be faulty, I swapped in an AGP S3 Virge
GX2 card which I knew to be working when I removed it from its
computer only a few months ago.

It was recognised as new hardware and the drivers all installed
properly. The computer said I had to reboot to get it to work.

When It had rebooted, the second monitor didn't work and it reported
the same Code 10 error.

So I took both graphics cards out, put the Nvidia card back in the AGP
port alone. It worked fine.

Then I put the S3 Trio card back in to a different PCI port, when it
loaded up the software was recognised and it installed... and then
both screens worked again.

I thought that had fixed it, but when the PC was next turned on it had
started giving Code 10 errors again on the Nvidia and I'm back to a
single desktop running via the PCI S3 Trio card, with the Nvidia
installed but not starting.

Trying to update drivers via device manager doesn't do anything, it
can't find any newer drivers.

Has anyone got any idea how I can fix this, apart from taking the PCI
card out and moving it to a different slot before turning the computer
on every day?

Travis