How to rename file extension?Normal:
To rename the file, you should first select it in Window's Explorer.
Then press "F2" on your keyboard and change the extension to .zip
(just type it in at the end of the filename).
Change Settings:
If this doesn't work, then it may be because Windows is set to hide the filename extensions.
Bring up the View menu (in Windows Explorer), and click "Folder Options...".
Select the "View" tab, and select "Hide file extensions for known file types".
The exact procedure may vary between different versions of Windows,
but have a look around and I'm sure you will find it. What is MP3?