1. Open Folder Options by clicking the Start button Picture of the Start button, clicking Control Panel, clicking Appearance and Personalization, and then clicking Folder Options.
2. Click the View tab, and then, under Advanced settings, do one of the following:
a) To show file name extensions, clear the Hide extensions for known file types check box, and then click OK.
b) To hide file name extensions, select the Hide extensions for known file types check box, and then click OK.