How to change (lost/unknown) local Windows Passwords

Beware! if the user account you are going to change the password on has EFS-encrypted files you will lose access to them until you remember the old password. This only applies to local user accounts and not domain accounts. In a properly setup forest/domain, the administrator can recover encrypted files for domain users.

With Backtrack / chntpw :

chntpw is a Linux utility to (re)set the password of any user that has a valid (local) account
on your WinNT or Win2000 system, by modifying the crypted password in the registry's SAM file.
You do not need to know the old password to set a new one.
It works offline (i.e., you have to shutdown your computer and boot off a linux floppy disk).
The bootdisk includes stuff to access NTFS partitions and scripts to glue the whole thing together.
This utility works with SYSKEY and includes the option to turn it off. A bootdisk image is provided.

Boot disk / Tools

- Stellar Phoenix Password Recovery : Simple startup utility resets a forgotten admin or users' password using a familiar Windows-like program interface instead of command-line.
- EBCD - Emergency Boot CD - Bootable CD, intended for system recovery in the case of software or hardware faults.
- SystemRescueCd
- Windows NT/2000 offline password editor : a utility to reset the password of any user that has a valid local account on your Windows system.
- List of live CD..