Tmpgenc xpress dvd encoder

i trying to make a avi file into a dvd useing tmpgenc xpress dvd encoder but at 50% complete it stops and i get a message that says invalid sample format and the encodeing stops.and how do i make the volume louder when makeing a a dvd movie i useing tmpgenc xpress encoder and my burning prgram is nero cause after i make a dvd i have to turn up my tv all the way to hear it