GameMinimizer is a freeware tray application that minimize full screen applications such as games to system tray by pressing a hotkey. In addition, GameMinimizer will minimize all windows when its tray icon double-clicked.
http://www.mystercrowley.com/files/GameMinimizer_v1.0.zip
http://www.mystercrowley.com/files/GameMinimizer_v1.0.zip