How to Rename a File Extension in Windows 7

1. Click the Windows 'Start' button; select the 'Control Panel' item.
2. Type 'folder options' in the search box located at the top-right corner of the Control Panel window.
3. Click the 'Folder Options' item that appears in the list of search results.
4. Select the 'View' tab located at the top of the resulting dialog box.
5. Uncheck the box labeled 'Hide extensions for known file types.'
6. Click 'Apply' to confirm the change but leave the dialog box open.
7. Navigate to the folder containing the file with the extension you want to rename.
8. Click the file once and then press the 'F2' key to select its name and extension for editing.
9. Rename the extension as needed, and then press the 'Enter' key. Click 'Yes' when prompted to confirm your change by Windows 7.
10. Return to the 'Folder Options' dialog box you left open in Step 6.
11. Check the 'Hide extensions for known file types' box and then click 'OK' to restore the default setting.