When watching DVDs, the extreme left and right edges will be cropped if the display is upscaling strictly in accordance with standards. That's because the first and last 8-9 pixels in each line are part of the nominal analogue blanking and should be assumed to not contain picture information.
If you are seeing the entire image on your computer monitor, the upscaling is being performed incorrectly.
HD content on the other hand does not contain these blanking regions and can be shown at 1:1 pixel mapping.