With windows 8, product keys/License keys are encrypted in the bios, not sure if all computers/laptops are being done this way, but my HP laptop with windows 8 are done in this way, no stickers with product keys like b4.
I have the asus s46cm and cannot find the win 8 product key.i have installed windows 7 but now could not find the key for the preloaded win 8.