Ophcrack is a Windows password cracker based on a time-memory trade-off
using rainbow tables.  This is a new variant of Hellman's original trade-off,
with better performance.  It recovers 99.9% of alphanumeric passwords in
seconds.  Features:

  - Runs on Windows, Linux, FreeBSD, and Mac OS X (x86)
  - Cracks LM and NTLM hashes
  - Free tables available for alphanumeric LM hashes
  - Loads hashes from local SAM, remote SAM
  - Loads hashes from encrypted SAM recovered from a Windows partition,
    Vista included

WWW: http://ophcrack.sourceforge.net/