Okay, hey buddy. You say that your Impossible Creatures folder is on your desktop, right?
When you open up My Computer, click C:\, and then click Program Files, there should be a folder called Microsoft Games. In that folder should be another folder called Impossible Creatures.
When you say you have your IC folder on your desktop, does that mean you do NOT have this folder in your C:\ directory?
If so, are you using a crack to play Impossible Creatures? That means you did not have to install it and you do not need a CD to play.
If you installed Impossible Creatures from a CD, there should be a folder where I said.