Some people are just retarded. .rar is archive but you can play them like a video file too. Right click on it and select open with and open it with VLC. If you don't have VLC, google it and download it.
Drop the file on Stuffit Expander and the vid will appear. (If the file is in parts 1, 2, 3, 4 etc have them all downloaded together so Stuffit can merge them.)