If using the VGA input...
Options...Priority...Normal (4:3)
If using the Component input...
Toggle through the available aspect ratios using the remote. It's one of the buttons at the upper right. Chances are 4:3 or ZOOM will work best for you.
Other than ZOOM mode with component...the AE100 16:9 capability is pretty useless with non-anamorphic widescreen source material if OAR is important to you...and it sounds like it is.
Make sure your DVD player thinks you have a widescreen TV.
Non-anamorphic widescreen source material is a pain and I try to avoid it!