I assume your computer screen is 16:9
And your TV is 4:3?
If so most dvd players have settings where you can choose how to display widescreen movies on a 4:3 TV,
what you want to do is called letterboxing, basically black bars are added to the top and bottom of the image to avoid cropping the edges of the video.
If your DVD player doesn't support this kind of feature, you might want to look into doing so when creating the DVD (this will include the top and bottom "black bars" in the video source itself)
Although this is something I never had to do before, I have no idea what software you could use to accomplish this.