The question is a bit too broad. You have to break it down further. What exactly is it that you are stuck at?
I once created a fake desktop using C2 (they could not show a real windows desktop for legal/copyright reasons). It was rather simple. Started with the background wallpaper, icons as sprites, and when clicked on some icons a window would pop up (also a sprite, with a drag & drop behaviour so that one could drag it around).