Thanks for nothing, Community. Drag and drop fail is fixed.
All I got when trying to drag photos and URLs to my desktop was a red circle-slash. Turns out Firefox is the only browser that insists on UAC being turned on, apparently a -no-deelevate problem — whatever that is. Despite three calls for help here, not a single person read my post. Of course, there's o Mozilla support.
A bigger revelation was that users are not allowed to uninstall Firefox. Requesting uninstall in Control Panel is not an option. Firefox only allows you to initiate a repair. Takes combing through every Mozilla and Firefox entry in App Data and RegEdit to get rid of this pest.
Enough. I've gone from Mozilla to Nozilla.
Upravil(a) MIchael Linder dňa