windows 7 Administrator PasswordBreak

Few days ago i change my windows -7 Administrator Password and my friend again change it and gone away . I try Following method and got Password reset. 

1. Start windows in DOS Mod 

2. at DOS Prompt i came on root (C:\>)

3. Check accounts by Typing c:\> net user and Press Enter 

4. User List 

5. Again C:\> net user Administrator Press Enter 

6. Again Enter To Reset Password

Start again computer and Administrator has no Password :)

If there is another way please share with me.