Seeing over double free disk space after moving files around...

I was going by the Properties window on the c: drive (see attachment). I also remembered I had WinDirStat installed. It's showing 173.9 GB free, it matches what Windows is reporting as well. I'm not understanding what happened. Just makes no sense.

What version of Avast are you using now, and did you recently do a program update ?
Secure Virtual Machines is the tool that causes the 50% bug.
It's possible your max storage was at 50% and changed to 3%.
If you don't know what it was at before, i don't think anyone can answer definitely if that is the problem.
In the Avast thread the OP reported Avast set System Restore space to 3%.
https://forum.avast.com/index.php?topic=174508.0

Do you have a recent cloned HD you could compare to ?

I'm running Avast 2015, and have been for several months. No program updates to Avast (if that's what you're asking). No new software installs of any kind for about three weeks).

I DO have one more drive that I keep in our safe deposit back at our bank that's about a month old, but I'd like to find out what is going on before I start messing aroud with that drive.

I went from about 77Gb to 173Gb after moving all the files around (but NOT deleting ANYTHING in the process).

Maybe you have an older Avast 2015 version ?

Version 2015.10.3.2223 is the release that should have fixed the 50% bug, apx. 2 weeks ago.
Latest version of Avast Antivirus

With the 50% bug, from what i have read, max space could get set up to 50%, and then later Avast might delete all restore points, and start over again ...

Version 2015.10.3.2225 was just released a couple of days ago.

It's possible Avast changed your free space, but i don't know how you can definitely say for sure with the info you have.