Double soundtrack in avi and dvd film

[Sarah35]

I`ve downloaded a few avi films for previewing before buying as I usually do, some of them have the talking as normal in films but some also have other voices in a foreign language in the back, both voices `talk` one before the other, it`s like I`m watching one film with 2 sound tracks or two films with one video, I`ve converted the avis to dvd using convertXtodvd and other programs but when played in my computer and my dvd player the two voices are still there, how can I get rid of the foreign one?, I can`t turn it off in my dvd player.