Croping videos??

is there any easy way to crop videos??
like when Im converting videos in to mp4 for the p800 usually the movie trailers are wide screen so the black part makes the video look very small....can i crop the video in vertual dub?? if yes then how?
i usually use adobe premear for croping videos but that takes sometime and it gets really irratating.....is there any simpler way
like helix producer can crop videos...