From console, you can run "fglrxinfo":
display: :0.0 screen: 0
OpenGL vendor string: ATI Technologies Inc.
OpenGL renderer string: ATI Mobility Radeon X1700
OpenGL version string: 2.0.6334 (8.34.
Note that in the last line you can see the version of driver (8.34.8 in this case). If you see something like "Mesa" as vendor/renderer, then probably you don't have driver installed correctly.