Thanks for looking into this. I got the game from Steam. In my game folder, there are no .txt-files with expansion names; However there is a folder called "DLC", and in it are lots of folders with names of the campaigns "GC39", GC40" etc.. 14 different in total, so I'm guess...

I got the Gold Edition on Steam recently, but the extra campaigns don't seem to be included. None of the steps above help. I see the icons (except the last folder) on the new game screen, but when I click them I'm told the "expansion is not installed. Do you want to purchase and install it now?...