Probably an old tip but some may find it interesting.I haven't fully explored it but you may want to play with it
Viewing/Changing File Associations through command.
You can run a command session and type "assoc.exe" press enter and you'll see the association assigned for that extension?
You can likewise change the association for it by entering "assoc.exe=txt" or whatever you would like to assign to it.
Or enter "assoc.exe=" and it'll have no association at all.
To set it back correctly: enter "assoc.exe=exefile".
That works on all other extensions as well of course.
To check all your assigned associations enter "assoc|more" and you'll get them all.
A list with the first 20 or so may just show up with "...more..." at the end.(on my pc anyways)
Just keep pressing or hold enter to make the list scroll aphabetically.