You will also need to be patched to the most current patch available. Do this by selecting the AutoUpdate on the startup page of your game.
You will also want to get the Community Expansion Pack.(CEP) Go here to read more about the CEP and find the link to the download. UPDATE: Version 1.01 can be found here after you read the previous thread that tells what the CEP is.
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UPDATE: You also need this second Hakpak for Escape from Undermountain:
http://www.ironworksforum.com/hosted...rahakv1.00.rar -- 72Mb (RAR compresses better)
http://www.ironworksforum.com/hosted...rahakv1.00.zip -- 99Mb
Make sure the hak files are in the hak folder and the tlk files are in the tlk folder.