For some file types, Windows Explorer displays a specific icon, while for other file types the generic icon is used. Explorer will display a file specific icon if this file type is registered. Most programs will register their data file types automatically when you either install the program or run the program for the first time. You can register file types or edit the registration information at any time manually from the Explorer.
1. Start Explorer
2. Select the Options command from the View menu and then click the File Types tab.
3. Press the New button for a new file type or select the file type and press the Edit button for an existing file type
4. Enter the type of data file in the description field and enter the extension in the extension field.
5. Press OK twice to confirm your selections.
For more information see: