First off id like to quote sickyourit
by default, after installing windows xp (PRO, although it's possible this happens on HOME as well) the default administrator password is.... you guessed it. Nothing
That cleary shows that we were talking about admin accounts not default shares.... Those are two different things. I also wouldnt exactly call them hidden because they are listed in the computer management mmc.

Now when you say you have used them in the recovery console are you talking about the administrative shares or the "blank" administrator password. If your administrative password is blank, then you know what needs to be done and I wont explain.