while booting pres the f8 button so u get them safe mode options ...
when u do that choose for Safe mode with command prompt
then when it starts ,, type in: "net user" without the quotes,, so u see which users u have on ur pc ..
then u pick a user,, in ur case its the Administrator then u type in the next: "net user 'username' *" .. NOTE* dont forget the star ..
then u type in the new administrator password ,,
let me know if it works .