Restore Show Desktop Icon to Quick Launch on Taskbar

Manual Fix

To re-create the Show desktop icon yourself, follow these steps:
Click Start, click Run, type notepad in the Open box, and then click OK.
Carefully copy and then paste the following text into the Notepad window:

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

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.