Click on the Export 
button.
Select "AVI" and click "Next" 
.
Since the aspect ratio of the output video is 4 x 3, and we want to keep the pixel aspect ratio to 1, let's change the size of 320x240.
Note: The size may be different for you. Calculate the height so it is 3/4 of the width.
Click on the "Next" to go to the next page.
There is no need to change anything here. Click on the "Next" to go to the next page.
Click on the "Browse" 
button and enter your file name in the standard file save dialog.
Click "OK". River Past Video Perspective will start conversion.
