How To Keep Audio Books Separated??
 

I'm trying to organize my files on my Blackberry 9300, and I've put the audio books in their audio book folder but because they are in .MP4 format they show up under videos and if I turn them into MP3 they come up with my music files. Which format do they need to be for them to stay separate?

What's the point of having different folders if the files won't stay in them :?