XnView Software

when you open the program after closing a big session
it asks if you want to reload the previous session and offers to save your choice
but the only option is OK
it should be a yes or no option

I have this problem often, I saw on this forum you can turn this off by hitting F11 , but it just turns it off for the selected image, if you navigate to another image, it will go fullscreen again.
When I turn off dual monitors in the settings, this setting comes back on.