Their is a free utility named Ophcrack which makes the whole process of discovering the logon password easy. Ophcrack is a free Windows password cracker based on rainbow tables. It is a very efficient implementation of rainbow tables done by the inventors of the method. It comes with a Graphical User Interface and can solve passwords up to 14 characters in length. All you have to do is :-
- Simply download the Ophcrack ISO from here and burn it to a CD
- Insert the CD into a machine you would like to gain access to, then press and hold the power button until the computer shuts down
- Turn the computer back on and enter BIOS at startup. Change the boot sequence to CD before HDD, then save and exit.
- Wait for the computer to restart and Ophcrack to load, all work done just save the password it gives you and try logging in with that password.