Aspect Ratio: circles - 720x480 and standard tv 4:3

[Cunhambebe]

Hi there!
I'm trying to fix something around here. I've got an animation showing Planet Neptune and a spaceship flying by. You might know that circles designed with pc resolution 720x480 appears as eggs when shown on tv (4:3). I've tried all pan and crop options with Vegas and the result is always the same: a blue egg.
In fact I read this in DVD Menu Studio help file:

1. Aspect ratio. First typical issue designer encounter is the aspect ratio. The Computer screen has square pixels while TV has rectangular. So if you design in the correct DVD specs 720x480 it will become stretched on TV


Circle designed in 720x480 = regular circle
Circle shown on 4:3 TV = egg

Does anyone know how I can fix that?
Thanks in advance!

[vitualis]

Design your animation or video in 4:3 pixel ratio as well (e.g., 800 x 600) and then resize that to 720 x 480.

Regards.