This is not a graphics driver issue. Once again, we're dealing with a PCI-E 2.1 graphics card being installed on a motherboard with a PCI-E 1.0/1.0a slot. And yes, you probably do need a BIOS update. Given the age of the board and the date of the last BIOS update (11/4/2008), it's possible the card will remain incompatible.
You need to go here
, select your OS, and expand the BIOS portion. The 0602 BIOS is the most recent, so download it. Also, in the BIOS-Utilities section, get the update tool.
Again, I am not certain this will enable compatibility with that video card. If it does, great. If not, consider an older generation, PCI-E 2.0 card, such as an HD4850 or something from nVidia.