Cyberat_88 :
Disable System Restore and reboot, on all drives.
Go to file explorer, view and select show hidden and system files & folders.
Find - System Volume Information - folder on the root of all drives involved and delete what's in them.
Enable System Restore and reboot, 1% usually does it for me, 2% if you're feeling generous. 12% is too much for large HDDs.
In following the above and coming to select "show hidden and system files", I got the warning "deleting or editing can make your computer inoperative". Ignoring that and proceeding on to "C:\System Volume" information I got a popup saying that it is "not accessible" and that "Access is Denied".
Being then stuck with that, I re-enabled and rebooted as instructed.
After that I found a restore point from a few minutes ago with the many previous restore points gone. After waiting a 1/2 hr for good measure I hit "Restore" and - lo and behold- it worked! Halleluja!
It seems that by disabling Restore, rebooting and enabling Restore again, all the old restore points in the inaccessible files had been deleted and the file cleared. The system worked again! I now have the memory set to 6%, I will leave it there as I am not pressed for space.
I like to thank you for the instructions and, although I could in the end not follow them through completely, they got me on the right track and enabled me to solve my problem.
Greetings from Raleigh, NC. ericgericg