There is a common security recommendation that one will improve domain or server security by renaming the builtin Administrator account. Some state this is a dramatic improvement in security. Supposedly by changing the name, you can hide this powerful account and improve security.
Names mean nothing.
All objects in NT have ID numbers. All accounts have SIDs. The SIDs can not be hidden. There are baby hacker tools which automate the process of determining which account is the builtin Administrator account. See SIDs for more information about SIDs.