Put in working vid card, go to cmos setup and write down what settings you have, ( there's utilities for this to print it, but can't remember any offhand). Boot up and remove any of the old vid drivers, and change display in device manager to standard vga, shut down after vga driver install.
With power off reset your cmos w/jumper or if it don't have 1 just pull the battery for 20 secs.
Restart w/new vid card, hopefully should work, go to setup and put back your old settings.
Make sure assign an irq for vid is enabled, vga pallette snooping is disabled, and any cacheing for video is disabled.
Hope it helps, good luck