Changing Aspect Ratio

Using Nero Vision version

I have a file which should be 16:9, but it is actually 4:3. When I select 16:9 in Nero Vision 4, it just shrinks both horizontal and vertical. This produces the same effect as seen on a wide screen TV when they transmit narrow picture – black borders on right and left – but with the same vertical stretch distortion of the original.

Is there any way to REALLY change the aspect ratio?