The free version will convert WMV, AVI and MPEG to AVI, MPEG, Windows Media or Real Media. The pro version also supports VCD, MPEG-2, Super VCD and DVD. More Information: Unlike movie film which is a sequence of images with a synchronized (interleaved) sound track printed on the film, digital movies are data files that contain complex mathematical information. Digital movies, like all other computer files, contain a file name and a file extension. The file extension, the characters following the last period in the file name, tell the operating system what software to use to open that particular file. The first few bytes of the digital movie file, called the header, tells the software how to open the movie including what codec* to use. Herein lies the rub. If a movie was created using a codec that you don't have or it was written specifically for a player that you don't have you can't see it.