you could probably take them to the small claims court and i guess you could win.
However, the cost would be quite high, and unless you know a laywer (which i guess you dont, otherwise i wouldnt be posting in this thread
) not worth it.
Try writing into the watchdog who deals with this issue (not sure of the name)
also, why didnt they replace the graphics card, update the drivers for your graphics card from the internet