Last Win7 update broke some stuff
Three days ago was the last ever Patch Tuesday for anybody still with Windows 7 but apparently, as I gathered from other places, it broke a few things. From the presence of a black background instead of a desktop wallpaper, to a "Windows is not genuine" message. Furthermore, the latest security rollup (KB4534310) seemed to be the root cause of it.
On the contrary, this didn't happen to me, probably because I have my desktop wallpaper stored in My Pictures (but more so in a subfolder of it). Guess I'm lucky, but were any of you affected by this?