Completely uninstall your video card drivers, use Driver Sweeper from Guru3D to make sure every trace of it is gone from your system and registry. Next, download the OMEGA version of your drivers for your Radeon video card from Guru3D and give that a whirl. Again, make sure you're running windowed mode and if necessary, try running the game in Win XP compatibility mode, maybe even Win 7 mode, launch the game as administrator.
Hope this helps, good luck!