Restore the Show Desktop icon to Quick Launch bar in Windows XP and Windows Vista

For Windows Vista
Download ShowDesktop.zip and save to Desktop. Unzip the archive and move the file Shows Desktop.lnk to the Quick Launch folder which is located here:
%Appdata%\Microsoft\Internet Explorer\Quick Launch
To quickly access the Quick Launch folder, type shell:Quick Launch in Start, Search box and press {ENTER}.
For Windows XP
Method 1: Manually re-create the Show Desktop icon
Click Start, Run, and type Notepad.exe. Copy the following contents to Notepad.
[Shell]
Command=2
IconFile=explorer.exe,3
[Taskbar]
Command=ToggleDesktop
Save the file as "Show Desktop.scf" (with quotes, in order to prevent Notepad from appending .txt extension). Now, drag the file to the Quick Launch Toolbar.
Method 2: Using the Regsvr32 command
Click Start, Run and type the following command:
regsvr32 /n /i:U shell32.dll
The Show Desktop icon file should be available now