The "Show Desktop" icon is missing from Windows 7 and it is replaced by Windows 7 Aero Peek but if you liked having the"Show Desktop" icon like I did then use the following method to get it back...I did and it works great.

http://www.gpsoftuk....showdesktop.asp

Also note that little vertical bar just to the right of the System Tray clock is now Win7's default Show Desktop icon. You can hover over it to make your current open windows transparent (with Aero anyway), or click it once to minimize all, then click again to maximize.

Use Aero Peek to preview the desktop has to be checked in Taskbar Properties for the hover to work, otherwise you have to click it as Bill said.