Mark off the part of the movie you want to save (slide the orange marker to the end point in the movie where you want to stop and choose cut) That will "split the movie into two parts. click on the part you want, right mouse and choose copy (ctrl c). On the mid bar there is a symbol of a movie reel, click that and choose "new movie". When the new movie time line opens, paste the contents into it. Now, just to make sure you only get that part of the movie, go back to the "movie reel" symbol and open the previous movie. (CTRL F4) will open the manage movie requester and ask if you want to "delete" the current movie.   This does NOT delete the movie from your computer, it just removes it from the current project. Say yes. Now you should have only the part of the movie you want to burn. Save AS a new name so it does not overwrite your project. Now you can burn it to DVD.
There may be a faster way to do this (anyone else got any ideas) but I know this works.