I've got the system preferences to put the discs to sleep when not in use, however, that only works on my MBP's system disc and not the mounted external disc. For whatever reason, it buzzes and runs all the time when not in use. Is there a backwards way I can go about forcing it to sleep when not in use? (It is used seldomly - only when I turn on itunes, but I like to keep it on and mounted all the time). Thanks.