Turn the computer on and keep tapping F8 until you get to the "Boot Menu" go to "Safe Mode" then log in as administrator. Go to Start > Run > CMD

Type the following

Code:
Net user [yourusernamehere] *
then type a password ( it won't show anything when your typing the password just don't mess up. Then press enter and enter the same password. It will say "You have successfully changed your password" or something like that.