Thank you for that advice "nammerbom"
Unfortunantly that did not work. After installing the Catalyst it told me there was a error and in the log it said:
AMD Display Driver
Final Status: Fail
Version of Item: 8.970.100.0000
Size: 90 Mbytes
And the error message read:
Error messages
Driver Install: the specified driver package was not installed for matching devices
Any more suggestions?