I had to log into the .cmd command the other day when I did that my ADmin user account had been corrupted, and I couldn't log in under it. I did the following:
1. I went into my wifes "STANDARD USER" account and clicked on the start button them typed: "CMD" without the quotes.
2. When the .cmd command line came up in the list I right clicked on it, then clicked on "Run as ADministrator. Then hit Enter.
3. Type: net user administrator /active:yes. Hit Enter.
4. The command line will tell you if you successfully enter the Syntax. If so at the next line type: "exit" (without the quotations)
Now you can go in and create another User Administrator account using your hidden Administrator.
5 Once created don't forget to go in undr your new user Admin account and re-hide your Built in Admin Account.