I changed my blog address, and did not check the box to disable the old address. I could not find a way afterward to disable the old address, so I transfered the old address to another email address of mine, and cannot access it without a password. How do I disable my old URL?
If you go into the dashboard on the old URL you can then set it to private at settings > privacy. I always suggest keeping sites and not deleting them in case you might want to use it again in the future. Once you delete a site, that URL is gone forever and no one, including you, can get it back.