Windows XP minimize all active windows
 

For users with Windowshttp://www.syschat.com/images/icons/windows.png key on their keyboards.

Press Windowshttp://www.syschat.com/images/icons/windows.png key and M (Win+M) to minimize all active windows. To undo press Windows key shift and M (Win+Shift+M)

For users without Windows key.

Press CTRL+ESC and then ALT+M