ok you download it from steam
the thing is think the mod was made for retrial CD version, steam made changes to it not quite the same version now, steam update is buggy i heard from others! sorry i never had delta force serials from steam before. you could try to get the Cd/ DVD version of the game.
DF2 pack link:
http://www.amazon.com/Action-Pack-Cl...=Delta+force+2
can't say much about the seller, buy as is all i can say! never buy a use Cd/DVD with Keycode 9 out 10 its no good. only buy new