How to view a computer file extension

To view the file extension of a single file for all versions of Windows follow the below steps.
Viewing the file extension of a single file

1. Right-click the file.
2. Click Properties.
3. In the Properties window, similar to what is shown below you should see the "Type of file:" this is the file type and extension. As can be seen in the below example this file is a TXT file with a .txt file extension and in this case opens with the Text Pad program.

Make windows display file extensions of all files
Users more familiar with computer files and file extensions may wish to view all computer file extensions to help with locating and browsing files. To do this follow the below steps for your version of Windows.

Windows 2000, XP, Vista, and 7 users
MS-DOS and Windows command line users
Windows 98 and ME users
Windows 95 users

Windows 2000, XP, Vista, and 7 users

1. In Windows 2000 or Windows XP open My Computer
2. Click Tools
3. Click Folder Options
4. Click View tab
5. Uncheck the box that says Hide file extensions for known file types.

Or

1. In Windows XP click on Start
2. Click Control Panel
3. Click Folder Options
4. Click View
5. Uncheck Hide extensions for known file type.

MS-DOS users

In MS-DOS when typing dir to list all files will also list any files with extensions.

Windows 98 and ME users

1. In Windows 98 or Windows ME open My Computer
2. Click View
3. Click Folder Options
4. Uncheck the box that says Hide file extensions for known file types.

Windows 95 users

1. In Windows 95 open My Computer
2. Click View
3. Click Options
4. Uncheck the box that says "Hide MS-DOS file extensions for files that are registered" and then click on apply and ok.