My question is where did you get the drivers from the AMD website or from the install disk. I have to wonder about what effect if any not having SP3 loaded. I believe July 2008 is when SP3 rolled out, but CCC 11.4 is the oldest set that I see with 6400 series support. Bad thing is 11.3 release notes are not available and 11.2 doesn't show support.
I would try and un-install AMD drivers. Here is some notes from the release notes. Talks about .Net 2.0 and it's SP1 being needed.
The AMD Catalyst software suite 11.4 contains the following:
- AMD display driver version 8.841
- AMD HydraVision for Windows® XP, Windows Vista® and Windows 7
- Southbridge / IXP Driver
- AMD Catalyst Control Center version 8.841
Important ! Caution !
- The AMD display driver and the AMD Catalyst Control Center can be downloaded independently of each other. However, for better stability and performance AMD recommends that both components be updated from the same AMD Catalyst release.
- The AMD Catalyst Control Center requires that the Microsoft® .NET Framework SP1 be installed for Windows XP and Windows Vista. Without .NET SP1 installed, the AMD Catalyst Control Center will not launch properly and the user will see an error message.
So give this a try and let me know. I run older version of Windows like 95, 98, ME and NT 4.0, 2000 & preview 8.1 all under Windows 8 Pro.
AMD A10-5800K, XFX 7850 Ultra OC Edition 975MHz, 16GB RAM, Win 8.1 Pro 64 bit, MSI 7778 motherboard, 500W PSU, HP P7-1235, CCC 13.12 WHQL