Using a dime a dozen, store bought preconfigured PC running Win 7, during the initial setup out of the box, when you are at the user name/ computer name screen, I initially typed in a user name, but then did a "cut", deleting that name and I just entered a password to see if it would let me do this.
To my surprise it did, advancing me to the next screen with just a password.
When I got to the actual login screen and just typed in the password, but it wouldn't let me login. I tried the original user name with the password, but that didn't work.
The solution from Comtrash was to do a restore process, effectively reloading their version of the O/S.
Is this some M$ glitch?