How to change or break the administrator password as well as the user password without using any 3rd party software in windows XP, Vista and Seven (w7)

First of all switch on your computer and login to your system  as  any user.
Then
1. Go to start menu    
2. Open the command prompt as administrator.
3. Change the directory as follows

          C:\windows\system32>

4. Type following command to know users accounts and types
          C:\windows\system32>net users
5. It shows you the users name and type.
6. Take any user name whose password you wants to change.
7. Type following command to change password.

    c:\windows\system32>net user "username" *

Then it will ask you to enter a new password for that user.

8. Follow the instruction and change the password.[see screenshot]