Windows 10 has almost completely stopped working today!

OK, I'm in a mess!
Today, my Windows 10 install has gone crazy! It will (eventually) boot to desktop, but immediately gives error about 'c:\windows\system32\config\systemprofile\Desktop' is not available.......
Nothing is working, there are no normal icons on the task bar, it is not validated, I can't type anything in, etc.
It responds to taps on trackpad, but takes about 2 minutes before anything comes up.
Can anyone suggest what on earth has happened and how I should start to resolve this?
Thanks.

It's the shit new Microsoft update, broke my PC too. Try going back to an earlier build, it fixed it for me:

How to Roll Back Builds and Uninstall Updates on Windows 10

Tried uninstalling updates, didn't work. Tried resetting PC, but got 'There was a problem resetting your PC' error!
What is happening is that it boots to desktop, and after about 5 minutes, anything using the trackpad is usable. However, the keyboard doesn't work in things like browser search bar, or the Start box, but it is recognised in places like the File Explorer search box, or in Settings search box.
Also, most of the icons in the bottom right of the task bar, like 'safely remove hardware' etc., are missing.
Don't know what to do. try making a bootable USB and attempt a repair?

I'm quite surprised no-one is able to offer any further help here. This forum is usually really quick with help.
I tried to reinstall Windows, but just got this! Any help at all?