I too had trouble like this and was tearing my hair out till I found this on the AMD Forum coutesy of Gr33nGecko
1. Download the WICU.
2. Uninstall everything related to ATI/AMD.
Control Panel -->> Services -->> AMD External Events Utility -->> Disable / Stop Service ..
Command Prompt with elevated permissions --> sc delete "AMD External Events Utility" ..
Reboot ..
3. Launch WICU and delete anything related to ATI/AMD/CCC.
4. Delete all ATI/AMD folders in "C:\Program Files" and "C:\Program Files (x86)".
5. While UAC is turned off (Vista/7 only) navigate to the "C:\Windows\Assembly" folder and delete any assemblies which have the public token key "90ba9c70f846762e". It is possible that you won't find any, but check it.
5. Reboot.
6. Install the Catalyst package again.
Initially I did every thing but remove the assemblies because I had 91 of them with that token key, but they appeared to be the key to success as everything is working really well now
Phil
