I guess that is the problem. There was no other drive using that number. I only use the one ext drive. Somehow it picked up that I was plugging in another drive so it gave me another drive no. When I went to change the drive number back it wouldn't give me the option as it thought the drive number was allocated to a separate drive.... 'hope that makes sense'. Not a major as I just rebuilt it to the new drive number but just a hassle...