AMD has a driver cleanup utilityhttp://sites.amd.com/us/game/downloads/Pages/catalyst-uninstall-utility.aspx
This standalone uninstallation utility will clean your system of any existing AMD Catalyst™ drivers to prepare your PC for the clean installation of a new driver version. Currently supports Windows 7 at this time.
After running the utility, a restart of the computer is required to fully remove driver files that may be in use during the uninstall process. Installing a new driver prior to a system restart may cause the operating system to not function properly.
Note: Do not use with Windows 8.