Either that, or you could set that in the TV itself.
My Tv allows this feature. Yours might as well. Of course, you do realize that to fit a 4:3 image onto a full 16:9 screen, it will involve "strecthing" the picture to meet the edges. And, since no TV or DVD player can just make up what was never recorded in the first place, everything will appear short and squat.
Me, personally, I would rather live with an undistorted picture and black bars on the side than live with a distorted picture, but YMMV.