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Ophcrack is one of the most popular password recovery tools. It's free (open source as well), cross platform, and very reliable. Ophcrack uses a solid implementation of rainbow tables that just happens to have been done by those who created the method.
Ophcrack runs on Windows, Linux/UNIX, and Mac. It cracks LM and NTLM hashes; has free tables for XP, Vista, and 7; includes a brute-force module for simple passwords; offers an audit mode and a CSV export; presents real-time graphs; has a LiveCD for easier (and more efficient) recovery; and dumps and loads hashes from encrypted SAM.
Windows Key can reset your Windows password for you. This is different from the other tools, in that it doesn't recover a list of user passwords or even recover from a file. Windows Key creates a bootable CD (or USB device) you can use to boot the machine and recover the password.