That subject is discussed in the A640 Advanced Camera User Guide on page 78.
But it does not mention that you can save the zoomed-in display as a separate file.
However almost any photo editing software will let you do this.
It is called a "crop".
Generally, you draw a rectangle around the area you want to keep and then you click "crop". That eliminates everything that is not in the rectangle. Then you do a "save as" and change the name of the file (to prevent overwriting the original file).
My question is this, I just found out on my camera that when you use the zoom lever control in playback you can make your picture closer. Is there a way I can save that close up? thanks terp