If you find that accidentally delete the extension of a file, or just receive it that way, but most know the file type, you can change manually such extension. To do this you must ensure that Windows allows you to see (and therefore change) the file extensions, this is seen with the naked eye when we make a single click on the file and once shaded you can see both the name and the file extension . Windows, by default, hides file extensions, if this is the case then we must follow the steps suggested by Microsoft page to display these extensions:

To show or hide file name extensions

1. To open Folder Options, click the Start> Control Panel  and finally Folder Options.
2. Click the View tab, and then click Advanced Settings, do one of the following:
   • To show file name extensions, clear the Hide file extensions for known file types, and then click OK.
   • To hide file name extensions, check the Hide file extensions for known file types, and then click OK.

Once displayed file extensions proceed to right click on the file and then ‘Rename’, This will shade the file name only (point to the left), what to do is move the cursor to the extension and type it or change it. Once this step is done, click outside the area of file icon and extension will be saved automatically, a pop-up message indicating that the file may become unusable and wondering if you are sure you want to change the extension, you just have to click accept.

This is the aspect of a file without extension

This is the aspect of a file with extension

Note: We must be especially careful when changing the file extension and the right for that file type, otherwise we can damage the file and even corrupt the records associated with that file type.

The same file with the wrong extension