If you can boot into Safe Mode and the main Administrator account isn't blocked ( The one that is hidden and only seen in safe mode ) then you can unlock the password.
Boot into safemode's administrator account, it normally doesn't have a password so just click it and log in.
When you're at the windows part, go to Start > Run and type control userpasswords2 and under the account you want to reset the password click it and press the "Reset password" part, enter what you want and you'll be able to log in under that password.