If the Show Desktop icon is deleted from Quick Launch on your windows, the procedure below will recreate the it.
Open Notepad / Text Document and enter the following text:

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

Save this file as Show Desktop.scf & then drag & drop the icon on the Quick Launch bar to create the icon on your quick launch 

Enjoy!!!!