If you are using Windows?

Do you just want to show the File extension or has Photoshop been lost as the default program which opens those file types?

 

To just show the file extension it would depend on which version of windows you use.

For Windows Vista, Windows 7, and Windows Server 2008

1. Start Windows Explorer, you can do this by opening up any folder.
2. Click Organize.
3. Click Folder and search options.
4. Click the View tab.
5. Scroll down until you see Hide extensions for known file types, un-check this line by clicking the check box.
6. Click OK

For Windows 2000, Windows XP, and Windows Server 2003

1. Start Windows Explorer, you can do this by opening up any folder.
2. Click Tools, and then click Folder Options.
3. Scroll down and then click Folder and search options.
4. Click the View tab.
5. Scroll down until you see Hide extensions for known file types, un-check this line by clicking the check box.
6. Click OK

For Windows 8
Open File Explorer
Click on the View tab
Check the box that says File name extensions