Ah! I finally found the Gentoo package that does this:
It is based on the same code as in the OP's reference to http://home.eunet.no/~pnordahl/ntpasswd/
I have found it is in my SabayonLinux 3.4f DVD based installation, but it is not on my 3.4 miniCD based installation. But I don't strictly remember if I installed it on one, or deleted it from the other.
I haven't used this package under Gentoo or Sabayon, but I have used other bootable CD's based on this package, and it has worked pretty well for resetting the password of Windows boxes where the owner or administrator lost or forgot the password.
It won't crack or guess the password. It will simply reset or blank out the password. Actually, I've only been successful at blanking out the password. I've had mixed results trying to set a different password.
Word of warning: This package is not intended to be stealthy. You should only use it with the express permission of the owner or administrator of the box you are applying this tool, because the chances are the owner or administrator will eventually figure out that someone has been mucking around with their passwords.