I have downloaded some dvd and they say it is incomplete and can't burn to a RW DVD but I can watch the entire movie on the computer..

ONce it's 100% downlded LW will move it to the LW downld folder (which by default is usually called Shared.) Yes sometimes a movie is 90+% downlded & you've got most of the movie & perhaps just missing the credits or something. It's up to you. If you decide to burn what you have then AFTER burning you can stop the downld & delete the file from the incomplete folder unless you wish to share it. I've had the experience of a video showing up as corrupt but it was fine to play. (Sometimes corrupt just means the superficial details of the filename or id3 tag has changed since it was initially started to downld.) So same applies.