Heres tons of Nvidia Bios, from the lowest geforce 3 to the FX 5900, theres tons of odd ones here.
heres a good website for both NVidia and ATI bios, mainly newer videocard like the X800 and 6800, but theres alot of FX bios there too.
and various flash utilities.
and this place has tons of ATI bios, to choose from.
like always flashing your card is your risk, you screw it up and it's your fault, not the wesbite you download the file from or anything else, cause no one made you try it.
if you find your card is screwed up, you can do various little things to fix it.
I like using this way to fix screwed up Nvidia flashes.
"Nvflash 4.42" use the command "nvflash -e"
that command will erase the epprom and let you start clean, when the bios is clean, you need a PCI videocard, in you PC along with the AGP card...
use the PCI card as your videocard, not the AGP.
then get back into nvflash and flash your card back to its original bios before you messed it up.
other then that, theres a whole forum here full of people willing to help, so just post in here
Extracting your bios to back it up
"nvflash.exe -b backup.rom"
Lastly-Extremely Useful Post for anyone looking to mod a 6800 bios, to be a 16p or 6 vs bios, without the need of always using rivatuner.
this is some hardcore bios modding, so make sure you actually know what your doing before attempting it.
if you screw up, just make sure you have a PCI videocard around, then use the command...
NVFlash -E to erase the messed up bios, and flash to your backup bios and maybe retry again, and make sure you did it all right.
it all looks pretty easy, but could be easy to overlook a small step.