Neal, I just went thru that a couple of weeks ago. 2nd time this year. It was probably Ransomeware that hit you. It's nasty and you can't do a thing but reinstall the OS. Or if you're near one, go to a Microsoft Store and let them do it. They can save everything you have after they get rid of the virus. It will cost you 49.99 but it's well worth it.

I go it from downloading a piece of software from a website I thought was safe.... and it usually is. When I did the install it took over and I was scrod. These AHs are hacking good sites and putting their crap in software files we download and think are safe.

And that's yet another reason to run Linux. No ransomware!

On my own system I did an install of the OS (I'm using 8.1)
Then I did an "image" out of it which goes into a USB key (I got a 128 Gb but the backup uses FAR LESS than this)

Every year I reinstall my system from the image.
All data/programs are stored in separate disks and the only needed thing is to update the drivers for the graphic card.

Re-imaging the disk from the USB is 5 minutes.
So all the install/configuration part is only done once.