Saw an answer for this for Ghost 14, but menu structure seems to have changed for 15 and I can't figure out the solution.
Changed USB drives last weekend. Backups are going to the correct drive, but in my "Home" backup destination window the old (now non-existant) drive is still showing as unavailable (duh) in the lower left and in Tools:Manage Backup destination:drives dropdown, the old drive is still one of the options. As I said, this drive is no longer hooked up to the network and contains no recovery points. How do I remove this old drive from this list and make it the default backup drive on the Home screen?
On the happy side 
the correct drive that is now housing my backups is still accessible via dropdown in both of these places. No intervention on my part is required to get my backups to run correctly (now that I am wired as opposed to wireless), but it would still be nice to clean up this issue by removing this old drive from Ghost's visibility. It's just plain not as pretty to open up ghost and have no nice pie chart show up in backup destinations until you click on the dropdown.
Also, as Ghost opens, it seems to take significantly longer as it seems to be looking for this now non-existant backup destination.
Minor issue, Maybe, but I would still like to keep things tidy and any solutions would be very much appreciated.
Thanks,
Ross
PS. For those of you who helped me on my previous "wired vs. wireless" thread, I blame you. " 
as I did convince my wife that I needed that larger hard drive so I could dedicate the smaller one to the laptop. It's the old drive that is now not connected that is causing me this issue.