You Had Me At EHLO... : Moving public folder replicas from Exchange 2000 to Exchange 2007:
"Exchange 2003 and Exchange 2007 will not let you delete a database that still has data within, but Exchange 2000 will. The only way to tell that the database is empty is to use Exchange 2000's System Manager and inspect the Public Folder Instances node under the public folder database object itself. When the right-hand side of the window lists no folders present (occasionally hit F5 to refresh), the database is empty and it's safe to remove it.
