Hi darklord
Welcome to the forums! Your questions has been raised several times before and I suggest you search the forums. SS2008 does not yet support the SS2006 add-on but the add-on will be converted later this year for use with SS2008. Please read this post:
http://www.shipsim.com/ShipSimForum/index.php/topic,796.msg17434.html#msg17434
Regards
groennegaard