This easy tutorial for XP  will show you how to have your “Show Desktop” icon on any where in your computer.  Also you could download the file by clicking download.

Steps:

1. Open “Notepad“
2. type:
   [Shell]
Command=2
IconFile=explorer.exe,3
[Taskbar]
Command=ToggleDesktop
3. Now, “Save As...“
4. File name “Show Desktop.scf“
5. Place your show desktop as desired