Have you had all your shortcuts change to one application icon? Apparently this can happen if the .lnk becomes corrupt, your applications are ok, and you can open up documents if you open them from within the applications, but if you change the default program it changes for all the files that are shortcuts or files of similar type.

Here’s a few links that can help.

https://superuser.com/questions/92869/how-to-reset-shortcuts-lnk-file-in-win7

https://www.sevenforums.com/tutorials/19449-default-file-type-associations-restore.html