Offline NT Password & Registry Editor, finally got an update last month after a 4 yr hiatus. The new version of this awesome bootdisk includes support for Win8.1 and a working ‘promote user to admin’ feature among other fixes and driver updates.

2 new commandline functions are:
samusrgrp: a command line tool to add users to groups or remove users from groups. Users and groups must be local (cannot be domain / AD). It can also list the groups with their members in several forms, the output can be used in scripts of course. Listing groups will also list domain users that are members of the group (if any), but it will not be able to look up the name, so it will be listed as a SID only.

sampasswd: Password reset from command line (scriptable) Or list users in SAM file in a few different formats.

More information on these new tools ::here::
The bootdisk can be ran from a floppy,CD, or USB and can be Download from http://pogostick.net/~pnh/ntpasswd/