Most installations of Windows hide file extensions by default. This is generally a good thing because inadvertently changing a file extension can cause Windows to have difficulty knowing how to open a file. Occasionally, though, it is helpful to be able to see the file extensions, and occasionally you may need to change the extension.
Follow these steps to turn on (or off) the viewing of file extensions:
- Open Windows Explorer
- Go to the Tools menu (if your menus aren't shown, press the Alt key and they will appear at the top of the window)
- Select 'Folder options...'
- Click on the 'View' tab
- Uncheck the option to 'Hide extensions for known file types' in the Advanced settings box
- Click 'OK'
(Repeat this process and recheck the box to hide the extensions later if desired.)
Now you should be able to see the extensions on all of your files. To change one, simply click on it the same way you rename a file, and you will be able to change the extension. Windows will warn you that this could be a bad thing, but you won't damage the file in any way by doing this, and you can change it back if it doesn't work. So go ahead and click OK. The worst that would happen is that Windows wouldn't know how to open the file properly with the wrong extension because it uses the file extension to associate files with the application that uses them.