i asked that many times in different forums (including this one), seems the product id is part of a map.
it's strange cause HTC gives you a discount code (after installing your free map you get the link) which you apparently can't use without having the map already.
really strange. i wanted to buy a map, too. but i don't see the point of having a discounct code which i can't use and therefore paying the full price.
i wrote to tomtom a few minutes ago, i will tell when/if they answer.
Samsung Galaxy S3
Sony XPERIA Ray
Nokia Lumia 800