I know this is an old thread: Dosbox messed up my computer HELP

but I'm putting this up here for anyone who happens to have this problem. It took me a while to fix.

This is a windows file association error
Follow the link below, download the file to your desktop, right click and select "merge." That should fix the problem.
https://appuals.com/fix-file-associations-windows-7-vista/

Some of my nieces and nephews somehow caused this problem HAHA!