There used to be something called Omega drivers for older Radeon gfx cards that effectively let you use newer drivers on older hardware but last time I had a AMD/ATI graphics card was back with the 4870. I would do a google search and see if there are any hacked (Sounds bad but not hacked in a bad way) drivers that you can use to fool games into thinking you have newer hardware. Unfortunately that wouldnt solve the issue of not meeting certain requirements like shader version and so on.
Out of interest, which gfx card do you have and have you attempted to update with the latest AMD drivers?
