how do you make viewing ratio bigger with xvid movies

I have downloaded some movies in xvid format and used intervideo windvdcreator2 to convert it to dvd format. Afer doing this the screen size is very small, and I have to use the zoom feature on the dvd player to get a half decent picture size. Is there a program that will allow me to change the screen ratio before I burn it to dvd? Thanks in advance for any info