Hi, I refresh my first 8.1 because Kaspersky gave me troubles updating: blocking keyboard and mouse from use.
Then after refresh, everything went nice.
Then booting from my old win 7, I copied a file into c:\program, it asked me a password. Then when I booted back on my 8.1 garbage can was corrupted. Then other softwares.
Then I did a reg clean. Then rebbot. Then Black screen.
No problem, I have restore point. They where all gone.
Black screen in safe mode too.
Try everything that work for others, everything MS propose. Nothing. Tryed 2 video cards.
REFREH... It was horrible. Most apps where damaged.

The good thing was the refresh keep the Library and all programs in c:\Windows.old. So if something is not in Library it's in Windows.old

I still do like 8.1 and do restore point, but I am sceptical. If There has been a way to reinstall the Nvidia drivers, or clean the reg from a boot disk it would probably work. But I never found any reg cleaner for boot disk.

Good luck with your's.