Re Error 0x80070091.....
Just 3 weeks ago I did a Restore point and got the above error, same as yours, Guitarman, right before my screen went black and my PC died. I put the error number into a good search engine and got the following.....
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
answers.microsoft.com
System Restore error 0x80070091
Jestoni Mac asked on March 17, 2017
Microsoft
Microsoft has identified an issue in Windows 10 where System Restore will fail to complete and will generate the following error:
Details:
System Restore failed while restoring the directory from the restore point.
Source: AppxStaging
Destination: %ProgramFiles%\WindowsApps
An unspecified error occurred during System Restore. (0x80070091)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Harold Fra replied on March 17, 2017
Microsoft
Updated (3/21/17)
Hi Jestoni,
We are currently investigating the issue and will update this thread when we have more information.
Advanced users can resolve the problem by trying one of the two options listed below:
Option 1: Rename the WindowsApps folder in Safe Mode
1. Boot into Safe Mode.
2. Right click on Start and click on Command Prompt (admin).
3. Type these commands below one by one.
• cd C:\Program Files
• takeown /f WindowsApps /r /d Y
• icacls WindowsApps /grant “%USERDOMAIN%\%USERNAME%”

F) /t
• attrib WindowsApps -h
• rename WindowsApps WindowsApps.old
4. Reboot back into Windows.
5. Run System Restore.
Option 2: Rename the WindowsApps folder from the Windows Recovery Environment (WinRE)
1.Boot into WinRE. To do this, click Start > Settings > Update & security > Recovery. Then under Advanced startup, click Restart now.
2.Click Troubleshoot > Advanced Options > Command Prompt. Enter your administrator password when prompted.
3.Type these commands, one by one: ◦cd C:\Program Files
◦attrib WindowsApps -h
◦rename WindowsApps WindowsAppsOld
4.Reboot Windows.
5.Run System Restore.
Regards.
~~~~~~~~~~~~~~~~~~~~~~~
Good luck. My windows 10 software didn't reload on a reboot and now I've got a black screen of death and my PC is no longer working.