"Am afraid lots of games do this nowadays. The DVD doesn't have the media on it, only the set up files."
I appreciate you responding to this, especially since this seems to be a Steam problem and not an Obsidian one. I tried getting technical support from Steam, but their only solution was to send me to this forum.
I purchased the game version specifically for the DVD. I inspected the media itself and it appears to have the full 6 gigabyte content that I am now downloading from Steam over several days. If you look at the link in the original post, you will see a disclaimer that the DVD version only works for a retail version and not a backup version. The media I got was in its original packaging and had a valid Product Unlock Key. Could this be a locally burned copy with an Obsidian media logo?