Windows update causing "desktop is unavailable" error

A couple weeks back, I was prompted to install a windows update. I accepted, and after it had installed and updated, I signed in to my account to find a black screen, and an error message saying:

C:\WINDOWS\system32\config\systemprofile\Desktop is unavailable. If this location is on this PC, make sure that the device or drive is connected or the disc is inserted, then try again. If the location is on a network, make sure that you're connected to the network or internet, then try again. If the location still can not be found, it might have been moved or deleted.

I have tried following guidance from other people, mostly suggesting to manually moving/creating a desktop folder through windows explorer, and opening task manager to run a new task etc. 

The problem with this is that nothing works: I cannot open windows explorer, I cannot open task manager, I cannot open the windows start bit in the bottom left using the windows key - I literally can't do anything. All I do is restart the computer, which causes the system to restore a previous version of windows.

This has been on a loop since the first time. I still get reminded every hour to do the update, which I know doesn't work. I try to ignore it but eventually it just shuts my computer down and installs it, which of course results in just restoring to a previous version of windows, at which point the computer works absolutely fine. 

I've tried using the windows update troubleshooter program, which says it has found an error and has "made changes to fix it", but the exact same problem occurs. 

Also, I get an error message after installing the update stating the code 0x80070015

I'm really not sure what to do as this is getting very disruptive, and no solutions have worked so far. I would appreciate any suggestions! TIA