[Hollywood]

Umm so what's the problem here? Changing the extension on most files will not damage your system. If a file opens with the wrong program, then just go into the files properties, change the association type, and if you want check off the box that opens all of those file types in that program. This will then apply the changes to any file with that extension. If you can't delete it because Windows won't let you, then just go into safe mode and delete the sumbitch. Easy as that.