How to change file extensions

[664a69be9a6cdwubwub]

How do I change the .zip extension to .ss2mod? If I right click and rename, it just renames the file and doesn't alter the file type - it still opens with my unzipper.

[664a69be9a8fcNameless Voice]

In Windows Explorer, go to the Tools menu and open Folder Options.
Flick to the View tab and untick the 'Hide extensions for known file types' box.
Hit apply, and mutter the mandatory curse at whatever Microsoft employee thought that would be a good idea.