Runing BioShock on older Video Cards
 

If you got a video card older than NVIDIA 6600 or ATI X1300 you are out of luck playing BioShock as the game requires Shader Model 3.0. A group of gamers have started converting the shaders to work on 2.0 cards like Geforce 5 series and ATI X800 cards. The textures can be sometimes a bit "off", but overall it makes the game RUN on your older system!

http://shadershock.tk/