Try burning avi using vso convertxdvd. If you have srt it will also be burned automatically.
But i've never heard of movies in iso format tho. Iso are cd/dvd image file. If it's really a movie then you can burn it straight to dvd using nero or isoburn. You can also try mounting the iso in the first hand to see it was really a movie. Mount it using daemon tools lite or alcohol 120%.

Betul, betul, betul.