Show Desktop is an application that lets you have the “Show Desktop” icon beside the clock and system tray on Windows XP and Vista like it’s on Windows 7.
It creates a small rectangular button at the right side of the user’s task bar, next to the clock, which, when clicked, allows the user to minimize all open windows or temporarily make them transparent so the user can “peek” at the desktop.
Show Desktop supports Aero for transparency when used on Vista. You can enable and disable transparency, tweak the width, and change the button function from minimizing all windows to toggling the desktop.
Show Desktop is free and portable application that works on both Windows XP and Windows Vista. It requires Windows .NET 3.5.