The local Administrator account becomes the domain Administrator account when you create a new domain.

Message error:
"The local Administrator account becomes the domain Administrator account when you create a new domain.  The new domain cannot be created because the local Administrator account password does not meet requirements.  Currently, a password is not required for the local Administrator account.  We recommend that you use the net user command-line tool with the /passwordreq:yes option to require a password for the account before you create the new domain; otherwise, a password will not be required for the domain Administrator account." 


For this case, i even tried to change the local admin password, then rebooted and promoted DCPROMO, and it was still not working.
Finally I just ran the command: NET USER Administrator password  and it worked.


It only applies to windows 2008 SP1.