Knoppix is a Live CD. It does not include the 3D drivers for your card (because, I believe of legal restrictions on the redistribution of the drivers, they are available freely but including them on Knoppix would compromise the freely redrisubitable nature of the disc because of the license that is included with them).

If you want a Live disc with drivers for your card I suggest Games Knoppix DVD, the most recet release (4.0.2, although not quite as up to date as Knoppix 4.0.2) does include ATI 3d drivers and tux racer. If you want an installed system I would suggest Debian and then installing the drivers from ATI.