When I launch the game, the sound test window appears with options to run the game in full-screen or windowed mode, either option asks me to insert the CD-ROM of the game. clearly I do not have a cd of this, as i bought it here. Solution?

You probably already have figured out the answer to this as it is an old post, but I thought I would post the answer here just in case anyone else has this problem too. (I just bought the game and I had the same problem). I contacted Support, and this is the solution which worked for me:

Right-click the game's App and select to Show Package Contents, go to Contents > Resources, right-click the InheritTheEarth.iso and select to Open with > Disk Image Mounter [I got the message that the Image was damaged/corrupted, even after re-installing the game, so I opened it anyway]. I then loaded the “Inherit the Earth” app from inside the new dmg [not sure if this step is necessary]. Afterwards, when re-loading the game I simply used the normal icon and it did not ask me for the CD-ROM anymore.