PRODUCT KEY for ms office on vista?

hi i recently bought a compaq 6720s with windows vista basic. It was an offer with AOL. Only trouble is i cannot find the product key. there is a sticker on the laptop with a product key sticker underneath but when entered this doesnt work. ive contacted aol and the response i got was that it was "a technical fault"!! so no help there then! can anyone help me find out the prod key or tell me what to do? much appreciated cheers Angela