How do I delete a backups.backupdb file that Time Machine can't
I don't know where to start with this story, so I'll just jump to the end. I have an old backup on my desktop. I tried to delete it with Time Machine, but nothing happened. I dragged it to the trash and tried to empty the trash, but it cannot be deleted. When I select either remove unlocked files or remove all, Trash simply closes. Apparently, my Admin credentials are insufficient.
I successfully deleted files and folders sequentially from bottom to top. The backups.backupdb folder now shows as empty, but there must be several hidden and locked files in it, because Trash lists 7 files. Since I can't get to them, I can't unlock them. I would move the file to an external drive and erase the drive, but I also can't move the backups.backupdb folder. It just copies instead. I am stumped.
MacBook Pro, OS X Yosemite (10.10.5)