It might also be worth trying the different video connections available on your DVD. I'm not sure which ones are available on your Polaroid, but most DVD players have at least a couple different connection options: Composite video (that yellow plug that goes with the red and white audio plugs), S-video, or Component video. If you have multiple connection options and your TV or receiver support those connections, it would be worth trying them to eliminate a variable.
I'll start with an easy one. Have you checked for a brightness control? Sometimes its in the menu, sometimes its a wheel on the side.
It might also be worth trying the different video connections available on your DVD. I'm not sure which ones are available on your Polaroid, but most DVD players have at least a couple different connection options: Composite video (that yellow plug that goes with the red and white audio plugs), S-video, or Component video. If you have multiple connection options and your TV or receiver support those connections, it would be worth trying them to eliminate a variable.