Such a simple solution: someone on the Firefox forum suggested right clicking and then "Run as Administrator"! MS support even had me download and reinstall Windows 10, to no avail.
I inadvertantly did a "reset" and lost all of my installed programs (apps), including Firefox and Chrome browsers, tax sofware, video editing software, etc. Now when I try to download and install them I get the error message "Can not create temp folder archive". I've tried booting in safe...