i had pretty much the same problem only not two different type of files for part 1 and part 2. i was using my window media player to try to watch the movie but it gave me the same response. i went back to the library and clicked on explore then right clicked the saved movie and opened with realplayer. it said i need to download some free stuff to be able to view my file, it helped me step by step and in a couple of minutes i was able to watch the movie no problem. my window media player still will not play those certain movies but my realplayer does and it didn't cost me anything.