root: unknown user

This problem occurs because the file /etc/master.passwd damaged

1. Start FreeBSD server
2. Enter key at boot loader
    At Welcome to FreeBSD! boot menu press spacebar key to pause default booting
    Type number 4 key (type 4 number) to boot into single user mode

3. Press Enter Key, When prompted Enter full pathname of shell or RETURN for /bin/sh:
4. You need to remount / (root) file system in read and write mode with mount command, type the following commands:
    # mount -u /
    # mount -a
5.restoring /etc/master.passwd
    #cp /var/backups/master.passwd.bak /etc/master.passwd
    #pwd_mkdb -C /etc/master.passwd
    #pwd_mkdb -p /etc/master.passwd
    #pwd_mkdb /etc/master.passwd
6. change the root password
    #passwd root
7. reboot ...

http://www.cyberciti.biz/tips/howto-freebsd-reset-recover-root-password.html

Lost password Windows 7

Just folow the following steps and everything will be ok:

1. Boot from Windows PE/RE and start the command prompt
2. Use the following command to create a copy of the Stick Keys application: copy c:/windows/system32/sethc.exe c:/ (where c is the drive letter where your OS is installed)
3. The next command will replace the Sticky Keys application with command prompt: copy /y c:/windows/system32/cmd.exe c:/windows/system32/sethc.exe
4. Reboot your computer and when you see the log-on screen and press Shift key five times.
5. Now you will see a command prompt window. Here you will use the following command: net user you_user_name new_password
6. That’s it. Now you can use your new password to log in.
7. Don’t forget to restore the Sticky Keys application:  copy /y c:/sethc.exe c:/windows/system32/sethc.exe.

   http://www.pctips3000.com/how-to-reset-your-administrator-password-in-windows-7/