I have been running CFS3 since november on the following ancient PC:
GeForce 2 Ultra (30.87 DX9)
62Gb HDD (CFS3 on separate partition)
27Gb HDD (Swap File)
settings 5 4 4 5 1 1024x768x32
After considerable fiddling (I am a systems engineer) the game runs fairly smoothly, or as smooth as 2k2 at any rate. So it would seem that the game can be played on old hardware, as long as you have 2 or 3 weeks to tune it! My problem with the game is its cold and rather uninvolving, so I won't be buying new hardware specifically for this product.