The calibre-debug blah-blah 'should' have gotten rid of calibre.exe in the open with list, but anything that revolves around Windows Open with is a PITA.
Is that second screen shot from Windows or something else (has nikos added something to xplorer˛
). I was using a third party Open With gadget on XP, but I got rid of it when I moved to Win 7 as it caused me all sorts of grief.
I would uninstall calibre, and then expunge all references to it in the registry, initially with a lightweight registry cleaner and then a check for 'calibre' in the registry editor. That won't touch calibre libraries and settings. Then check to make sure calibre.exe has disappeared from Open With. I'm pretty sure that Kovid has removed the install feature that added calibre.exe to Windows Open With list, but I can't recall when he did it.
However, given you're on Win 7 and locked into using calibre 3.48 you might want to consider using Calibre Portable - it won't do anything to Windows 'anything' - i.e. it's self contained. The only downside is that it's the 32 bit version, and the only meaningful restriction that imposes is on conversion of large/complex books. And because you're locked into 3.48, that can be easily overcome - later.
Once you've installed calibre, in the
Windows Open With select another program option, browse to the directory where calibre is installed, select ebook-viewer.exe and make it the default program for epubs.
BR