Verified answer

picasa and its available at picasa.com it even saves a picture of the before in case you screw up on it.

Open the AFTER picture in Paint. Press CTRL+A, then CTRL+C. This will select all, then copy to clipboard.

Now open the BEFORE picture. Click Image>Attributes. In the 2 boxes, enter a larger number, say 2000, 2000. Hit OK. This will make the canvas larger. Press CTRL+V to paste, but don't click anywhere... now use the mouse to drag your AFTER picture over to the right side of the before picture. When they're lined up, you must use the mouse to shrink the canvas back down by clicking on the little grey square in the bottom right corner of the canvas and dragging.

Adobe Photoshop open both the pics, drag one onto another, crop it and resize, and drag to the others side. DOne