Below are steps.
- Boot your Windows Machine from installation media.
- Go to Repair Your Computer and Choose Command Prompt.
- Issue following commands.
move c:\windows\system32\utilman.exe c:\windows\system32\1234.exe.bak copy c:\windows\system32\cmd.exe c:\windows\system32\utilman.exe
- Reboot Machine and after you see Windows Login prompt press (Windows Key + U) to open a Command Prompt and type following command.
C:\> net user Administrator NewPassword
- Now login with new password.
That’s All !