If you're working with chapters, the movie will always keep playing after the selected chapter is done. You might want to consider breaking up your project into separate movies and compile them all on one disc into a multi-movie project. This way, you get to decide in the DVD-authoring process what action should be taken at the end of each movie. (You need to right-click on the image for a movie in the DVD menu preview screen and bring up the "Properties" window.)