Don,
On a PC (if you connect the AUDYA 4 such that you can view the contents of it's HD on your PC, you can rename or renumber the registrations - you cannot edit the 'contents' of each Register. To edit a Registration, you would have to go to the AUDYA 4, call up that registration, made changes to it/edit and then save with the same name to over-write the previous/old settings.
Hope this helps.
Thanks,
AJ