The user "administrator" is disabled by default in Windows Vista and later.  You shouldn't have any reason to enable/login as "administrator" and can safely leave it disabled and unused.  What are you trying to do?
I just got a new win 7 machine, during the setup it did not ask me for an admin password, only a password for my user name.  When i try and logon as the administrator and leave the password blank, it just keeps asking me for a password. Tried my user password and still nothing. Has anyone else ran into this issue? Not sure if i can ad a user named "administrator" and that would do the trick?  thanks
windows 7 admin password