Installing the game.

I received a licensed copy of the game as a gift (the main game 5 + the "Hammers of Fate" expansion). I installed both, and downloaded patches 1.6 and 2.1. I installed the patches. The main game runs fine, but "Hammers of Fate" displays the message: "Game disc not found... please insert the disc." I searched through all the topics, but there was no answer to this problem. Can you tell me what I did wrong or what I didn't do? I've already played the main game (a pirated copy), and I really want to play the sequel.