I got the problem after applying Windows 10 Anniversary Update on 6 Aug. 2016. The sign-in screen used show "lighted Window" and for lock screen I set my favorite image. But now both screen got the same one , lock screen image ! Can I got back the old lighted-window image on sign-in screen different from the one on lock-screen ? The changer made emergency stop after I selected the image for sign-in screen though the version is 1.2.1!