I have found in the past when all else fails, the drivers from this lot:
http://www.omegadrivers.net/
are pretty good.
I tend to stick to nvidia cards these days, only as in my own case studies over 5 years, i found them to be less troublesome to work with.
(note I say
less)
If its an AGP card you can't put it into another slot, if its a pci card then yes it could be an irq conflict (back in the good old days of DOS, windows 3.1 etc they kept me busy)
although XP is
supposed to handle that by itself.
Best way to check is to remove all cards (except the graphics card) reboot and see what happens. its also possible your card has developed a fault, and i would not rule that out either.......
but do give the Omega drivers a try, they have worked for me in the past :lol: