Guidelines for using BUILTIN groups and the local administrator account
There are certain guidelines you should keep in mind when you use BUILTIN groups and the local administrator account. For example, you can rename the local administrator account, but you cannot delete this account.
The Administrator account can be renamed but cannot be deleted.
The Administrator account cannot be removed from the BUILTIN\Administrators group.
BUILTIN groups can be renamed but cannot be deleted.
After the BUILTIN group is renamed, another local object can be created with the well-known name; however, the object is assigned a new RID.
There is no local Guest account.