How to Hide or Show File Extensions in Windows

As it comes out of the box, Windows does not display filename extensions. Typically, only unassociated files reveal their extensions. Otherwise, when you peer into a folder window, you don’t see the extensions for files that are associated with programs.

If you are detail oriented or just prefer to see all the filename extensions, you can direct Windows to be more forthcoming about filename extensions.

To display filename extensions, heed these steps:

1. Open the Control Panel.

   
   



2. Open the Folder Options dialog box.

   
   
   
   

   • In Windows 7 and Windows Vista, choose the Appearance and Personalization heading and then choose Folder Options.

     
     
   
   

   • In Windows XP, open the Folder Options icon.

     
     
   
   
   
   



3. Click the View tab in the Folder Options dialog box.

   
   



4. Remove the check mark by the item Hide Extensions for Known File Types.

   
   



5. Click OK.

   
   



6. Close the Control Panel window.

   
   

Filename extensions are now displayed in every folder window. That makes them easier to see but also adds another dimension to the filename: You now see the extension as you save and open files.

Don’t change a file extension when you use the Save As dialog box to save something to the PC’s storage system.

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Source:http://www.dummies.com/how-to/content/how-to-hide-or-show-file-extensions-in-windows.html