Flash BIOS files for GPU's are for mods such as increasing/decreasing clock settings.
There is a section here with the various ROMs for the 79xx series GPUs.
If your getting artifacts then most likely your GPU is already fried, and you can try to down clock the card, but replacement is more likely the option your looking at.
Can you be a bit more specific on the issues your having
Is it lines up/down the display in the same spot or garbled crap all over ?
If it is lines up/down in the same spot all the time it more likely your Screen.