Power2Go uses the DVD NTSC standard (North America) or PAL (for the rest of the world). Power2Go doesn't, as far as I can see, support other aspect ratios, such as 16:9 widescreen.
So when you burn a DVD it is going to force and flag any content as 4:3 (for NTSC) aspect ratio. To maintain an aspect ratio that's different than that, you'd have to pre-convert to 4:3 using another software program (like free MediaCoder).
If you are working with a video that is originally PAL, try the PAL settings in Power2Go.............but only if you plan to play it back on a PAL system.