HACK PASSWORD OF ANY OS

Windows-
1. By manualy injecting the cmd.exe inplace of utilman.exe.
          a. For this, we need a linux livecd which is able to mount the parttion. We take Backtrack3 livecd.
          b. now boot the livecd.
          c. Mount the c partition-
              ->ls dev (it will list all device connecting,from here we get the name of c partiton as sda1 or sda2
              ->mkdir /mnt/sda1 (it will create the mount device direcotry)
              ->mount /dev/sda1 /mnt/sda1 (for mounting)
              ->umount /mnt/sda1 (for unmounting)
          d. Go to the windows directory, rename utilman.exe to utilman.old and copy cmd.exe as utilman.exe.
          e. Now boot up windows. At the time of login screen, press WIN+U, it will prompt cmd prompt.
          f. type this cmd to reset password-
               -> netuser [username] [new password]

2. By using Konboot to bypass the password.

3. By using ESR_PRO livecd to reset the password.

Linux-

1. By using konboot -
2. By using command-

To change the password, 

  a. turn on the computer and press the ESC key when GRUB appears. Scroll down and highlight ‘Recovery   Mode’ and press the ‘B’ key; this will cause you to enter ‘Single User Mode’.

  b.You’re now at the prompt, and logged in as ‘root’ by default. Type ‘passwd’ and then choose a new password. This will change the root password to whatever you enter. If you’re interested in only gaining access to a single account on the system, however, then type ‘passwd username’ replacing ‘username’ with the login name for the account you would like to alter the password for.

Mac-
If the Mac runs OS X 10.4, then you only need the installation CD. Insert it into the computer, reboot. When it starts up, select UTILITIES > RESET PASSWORD. Choose a new password and then use that to log in.

If the Mac runs OS X 10.5, restart the computer and press COMMAND + S. When at the prompt, type:

fsck -fy

mount -uw /

launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist

dscl . -passwd /Users/UserName newpassword