I will explain here how I solved this stupid problem that came up in Windows 10 . Having a huge number of photographs to view, choose and edit, I decided to install the Irfanview freeware program, which I have known since Windows prehistory and had never given me problems . But with Windows 10, the story was a little different! I decided to uninstall Irfanview after completing the above tasks, perhaps because it seems really prehistoric. The uninstallation program warned me about the return of the file associations to default and I thought everything was fine. The problem came out when I tried to re-link the image files to my preferred viewer ( the old school Windows Photo Viewer ). When I tried to choose " open with " and " choose another app ", there was not the expected " always use this app to open .jpeg files "! After hours of reading messages from people with the same problem to solve, I came to the conclusion that Irfanview ruins severa...