A file name extension is a set of characters added to the end of a file name that find out which program should open it. By default, Windows Explorer hides file

name extension in Windows 7 and also earlier versions of Windows. Every program that’s installed on your computer is designed to open one or more particular file types, each of which is identified by a file name extension. It is recommended for safety reasons to show the file extensions. A lot of hackers can trap you by sending to you virus files with .exe extension

1. Go to Start menu and click on Control Panel
2. From control panel window click on Folder Options icon
3. If Folder Options is not available, change View by to Large icons at the top right of the Control Panel
4. Then click on the View tab from the folder option dialog box
5. Next scroll down until you notice Hide extensions for known file types, un-check this line by clicking the check box
6. Click OK to save the changes

If you want to hide file extensions again, then click on the Hide extensions for known file types check box, and then click OK