What happens if you change the extension of the files?

Answer 1

The only thing that willl happen is that the file will be associated with a different application program, however, the data (and file type) will still remain the same. For instance if you took a JPEG photo and changed the file extension from .jpg to .doc it would become associated with MS Word and prompt MS Word to launch if you double clicked on the file.

But when word comes up, it will give you an error stating that its not an acceptable file type. If you took that same file and attempted to open it in a graphical editing program such as Photoshop, even though it has the .doc extension it will still come up without a problem.