Enable hidden admin as regular user?

Hey all, I just bought a used computer for my girlfriend, but it was not reset. Her account has no admin privileges and the admin account is password protected. Is there a back door on 64 bit vista to enable the hidden administrator account?

(I'm going to assume that you have actually purchased this computer and thus all recommendations are for legal purposes )

Well... there's a couple ways to go about this. You can use something like ophcrack to brute-force the password (I have used this with great success). You could also reset the password with a tool like this. It really just depends on how you want to go about it.