I think on this machine I never had Irfan - this was on the previous machine. Revo Uninstaller is good at finding leftovers, and it doesn't see it.

Oddly, when I typed "Irfanview" in Start Menu Search, a folder popped up - Vuescan 2014, with files vuescan.ini and vuescan.log - leftovers after I tried Vuescan driver to revive the HP scanner. And.... Revo couldn't find it.

Could be this, and could be something else. Will see.
Backup utility "Second Copy 8" might be causing problems - works with Win 10 but it is at least 2 years old. I like it, wouldn't want to replace, and Second Copy 9 is not free.