Every now and then my desktop icon that I like to have in the quick launch on the Windows desktop stops working properly. You can replace it by going to Explorer and right-click dragging it to the quick launch but when you use it, it just opens the desktop as a folder not as your full screen desktop.  So once again I’ve looked it up and found this site: http://support.microsoft.com/kb/190355#FixItForMeAlways which fixes it for me.  Just in case this site is someday not available, here are the step by step instructions also:

To re-create the Show desktop icon yourself, follow these steps:

– Copy these four lines of text
(Select them and press Ctrl-C)

[Shell] Command=2
IconFile=explorer.exe,3[Taskbar] Command=ToggleDesktop

-Open Notepad and paste (Ctrl-V) the text into the Notepad window:
(be careful to delete any spaces at the beginning of the lines)

-On the File menu, click Save As, and then save the file to your desktop as Show desktop.scf.

The Show desktop icon is created on your desktop.

-Click and then drag the Show desktop icon to your Quick Launch toolbar or your Task Bar..