Hi Mikko,
if you have deleted the media item from the usb then you can call up that number (using the keypad entry method) when the system tries to load it the media store will recognize that it is gone and allow you to "free up" that entry number for use with a new media item.
Further if you want to make it even easier you can delete the MediaDatabase file that is on the USB. This will trigger it to start from scratch completely the next time you plug in the usb drive. Just make sure that the computer you plug it into has View all files set. The MediaDatabase is set as a hidden file (has a period in front of the name).
Les
#Carbonite