If you have a movie file or several images in a .rar file, I would use UnrarX to extract the information from it. Launch UnrarX and go to the preferences and click "Save incomplete extracts" or something like that. I have used it to extract a lot of stuff. However, it you have a plurality of .rar files from one file (e.g. .rar001, .rar002, .rar003), then you will need the first file (.rar001) and subsequent files after that in order to open the archive.