Hello Merlin, I updated to Win 10 last Aug. 2015, had problems and went back to Win 7. Went back to Win 10 again and more problems, so I settled back to Win 7.
In reading your post, I agree with you that for awhile I had duplicate files
in C disk. These are now long gone.
However, I still have a bunch of duplicate files on my backup disk D only. They are small in size and are dated Oct 25 and Oct 30, 2015. then Jan 9, 2016
(date of my last OS change from Win 10 to Win 7.)
I have read to just leave these files alone since they could affect one's OS. My question is since all these