text: how to change a file extension for a file aftre it was made? used to change the extension to any file on windows by just using rename ? now renaming change the anme but not the extension even if i insert a dot. for example: car.jpeg , if i click rename and change to car.png , it will still be car.png.jpeg , that is : still in jpeg format. how to chaange an extension to a file already created. you have to set windows to display file extensions for known file types, otherwise it will treat your renaming attempts as trying to change the file name, not the extension.  open any folder.  from the folder toolbar, pull down tools and select folder options.  click on the view tab and uncheck the box marked hide extensions for known file types. then click ok.  your renames should then work as you expect.