If it's an actual video file instead of .rar files, there's a slight chance you've downloaded the first chunk and the last chunk of the avi file and therefore you can watch it with video players such as VideoLAN/VirtualDub.
Hi all, found a way, I just had to take the bitcomet extension off (.bc) example; movie.avi.bc, change this to movie.avi I had to open in my ftp client b/c I could'nt see the .bc extension w/out it.