Yes Simon, I didn't know that before. I thought that, when it is 16:9, that means only not 4:3, and that there are only those two aspect ratios.
In the "video perspective" program, it shows the other options: 2:11, 2:35, 16:9, and 4:3. I never knew the first two.
In DivX you have what is called: the original aspect, Wide Screen (16:9), 4:3, custom aspect and free aspect.
When I put this file on "Custom Aspect", it tells me that the current window is 720:576, and it gives me the choice to suggest another aspect ratio.