I was searching the Internet for information why Mechwarrior Online does not use my Radeon 6950 in 100%. I found information that downgrading amd/ati radeon drivers to 12.10 version (I had 13.12 ver) may help. So I uninstalled 13.12 from “Add or Remove programs” then downloaded 12.10 version and installed it. Unfortunately that operation totally destabilized my PC... After long investigation I found that this downgrade had broken my Direct3D. But the symptoms was really strange:
  • While launching steam there was “Steam client bootstrapper has stopped working” error
  • I couldn't start Mechwarrior Online. The launcher was starting but after clicking “Play” nothing was happening.
  • Launching “dxdiag” was giving “DxDiag has detected that there might have been a problem accessing Direct3D” error.
I realized that this last one is a major issue. Uncle Google said that there is no option to reinstall DirectX neither the Direct3D. Only tips was to update them to the newest version. Unfortunately I had the newest version so the installer didn't want to update a thing. Reinstalling drivers and many other things didn't help neither.

Workaround

The funny thing is that there is a workaraound for this problem. I could run everything properly in “Windows 7 compatibility mode” plus “Run as administrator”. Steam, Mechwarrior Online, everything was working.

Solution

The only thing that really solved the issue was Display Driver Uninstaller.
  1. Download DDU (I used 10.0 version from here)
  2. Uninstall the AMD/ATI radeon drivers through the “Add or remove programs”
  3. Restart your system into safe mode
  4. Use the downloaded DDU to clear your system from any AMD/ATI files
After restart you should be able to run DxDiag without any errors. That means the problem is solved. You can now safely install any version of AMD/ATI drivers.

If you, after downgrading your drivers, also have problems with running Catalyst Control Centre you can see this post.