Yes, if you have 'active directory domain services' (
adds) installed then your local administrator account has been upgraded to a domain administrator and you can't log into the machine as the local administrator because that user name | password combination doesn't currently exist.
Not sure why you would want to do this as the Domain Administrator is a member of the Local Administrators Group
Good point… depending on what you want to achieve… an local account wouldn't have permission to do jack on a server running adds any way.
p.s. Standard (
un-official) practice on Windows servers is to create a new local account with administrator permissions eg,
john smith and password = john before...