Windows Explorer Erratic Behavior Renders Computer Useless  

Kyhi's boot disk eh? OK i'll give it a go and report back.

I will also try to create a new user with the command line, as that's one of the few things that I can actually access.

bulshoy said:

I will also try to create a new user with the command line, as that's one of the few things that I can actually access.

That should also give you the ability to enable the built-in Administrator account and try that too.
Enable or Disable Elevated Administrator account in Windows 10
If you can't do it from its own command prompt, see Option Five to do it by booting from a Windows 10 installation USB or recovery drive.