Discussion about the "Hammers of Fate" expansion.

Hello everyone, please don't criticize me if I posted this in the wrong place; moderators, please move it if necessary. The problem is this: I finally got around to playing Hammers of Fate after finishing Heroes of Might and Magic V. So, I bought the licensed version, looking forward to new battles. I insert the disc, click "install," and nothing happens. The error message says: "Heroes of Might and Magic V is not installed, or a different language version is installed. The expansion cannot be installed. Please install the correct version of the game and then install this expansion." What should I do? Please advise.