Strange GPU problem

[JortC]

I have recently upgraded a PC from Windows 7 to 8.1.
Ever since, I've been having weird problems with my GPU (ATI Radeon HD 4770). Every application that requires above average GPU processing power crashes or prompts that 3D functions are not available.
According to the device manager, I am already running the most up to date driver.
And I ran the UI-less Windows Experience Index scan, which gave my GPU a score of 7,1.
I'm completely clueless as to what is going on here. Because of this issue, I cannot use any of the NIK plugins for Photoshop anymore, which are must-haves for me 🙁
Edit: I have also run a few OpenGL benchmark tests, and they all instantly crash when I run them:
http://www.geeks3d.com/20140304/gputest-0-7-0-opengl-benchmark-win-linux-osx-new-fp64-opengl-4-test-and-online-gpu-database/#download

Does anyone have any ideas on what could be wrong, or what I could try?

Thanks!

 

[NightAntilli]

Upgrading causes problems in general. You can try removing every single AMD driver on your PC, and re-installing them to see if that helps. Otherwise there isn't much you can do, other than re-installing windows completely.