However, if you still need this option in Windows 7, there is a freeware tool called Show Desktop (There are manual methods to do this, but required some skills) that will minimizes all open windows to display the desktop.
Show Desktop was created for Windows 7 but also works as a replacement for Windows Show Desktop icon in the taskbar on Windows 2000, XP and Vista also.
Usage: Just install the program and drag the ‘Show desktop’ icon the taskbar, that’s all.
Requirements: Windows 2000, XP, Vista or Windows 7 (Works on both 32-bit & 64-bit operating systems). Download Show Desktop