In this article we are exactly going to tell you the same.
To hack or Bypass windows passwords is not a difficult task actually. If you have the required tools you can easily bypass windows password.
However we highly discourages the use of blackhat hacking techniques and use this knowledge only for a good reason. Say you forgot your computer’s password and want to recover it, you may use this method.
Now coming back to the main topic again:-
We are going to use a tool called Hirens Boot CD to crack windows passwords.
Download Hirens boot cd from 
Q) Where are windows password saved?
A) Windows first encrypts the password using some algorithm and then saves it to a Sam file.This sam file is locked and no user account including the administrator can use this file.This file is located in windows/system32/config.
Q) What is the above link ?
A) The link given above is the download link for “hirens boot cd “.
It is a special type of live cd bunched with popular and useful freeware tools .The link is to hirens boot cd 15.1 ,but you can download any earlier version.
The main reason for choosing this cd is that it contains number of useful softwares.There are many other Live cds too ,you can even try them.
Q) what is a live cd?
A) Live cd is a cd/dvd or any other portable media containing bootable Operating system.These media have the unique ability to run operating system without altering the files and operating system installed on the hard disk of the pc.
It generally places it files in the Ram[random access memory ,volatile memory],so when a pc is rebooted all it files are deleted automatically.
Q) How does this cd helps us?
A) Since this live cd doesnt use the pre installed operating system ,we can edit/delete files [even the locked ones ie sam file].You can also use utilities present in this cd to change the windows password.
Steps to use Hirens Boot CD to Hack Windows Password:-
1 ) Download the zip file from the above link.
2 ) Extract it.
3 ) There will be a .iso file . Burn that file to cd using nero/poweriso or anyother software you have.
4 ) Boot using this cd ie insert this cd in CD-Rom and restart [Make sure that cd-rom has the highest boot priority]
5 ) After booting ,It will show a menu , Choose “Mini windows xp”.It will take some time to launch.
6 ) After it is finished ,You will be having a windows classic style desktop.
7 ) Click on start>>Hiren boot cd menu [HBCD menu]
8 ) It will open a dialogue box,click on “Menu” >>click on “password and keys”, there you will be having a list of softwares,click on “”Password renew””.
9 ) Now click on select target ,Browse to your windows ie “c:windows” and press ok.
10 ) Click on “Renew exisiting user password” and then choose the Your user account .
11 ) Enter the desired passw
ord and hit install.
12 ) You are now done just restart Your pc and login using your new password.
Prevention :
In the Bios settings set the minimum boot priority for removable devices . In this way the CD?DVD/USB wont boot and the method specified above wont work . Also set the password at the BIOS  so no one will be able to change the Boot settings .

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