If you are wondering where the "Show desktop" button is in the Windows 7 finish reading this. Although the Show Desktop icon which located inside the Quick Launch Bar have been made obsolete and removed from Windows 7, the Show Desktop function is still been retained in different location and can still be used, and does exactly what Show Desktop does. In order to quickly show desktop in Windows 7, just click on the Show Desktop bar at the  right end of the Windows Taskbar and notification area, which is next to the data and time clock (if you don’t hide the clock system icons in notification area). See illustration below for the exact location.

Mouse option: Press "Windows logo button "+D

The Show Desktop in Windows 7 also has a feature called Desktop Preview, the Aero Peek, that temporarily make all opened windows on the Windows 7 desktop transparent when you point the mouse over the “Show Desktop” button at the right end of the taskbar, all this without leaving your current window behind.

Other features of Windows 7:

Point to a taskbar (that familiar horizontal strip at the bottom of your desktop where your open files and programs appear) button to see a thumbnail preview of that window, and point your mouse to that thumbnail to preview the window full-screen. Then, if you  decide you want to switch to the window you’re previewing, just click the thumbnail. You can even pause or stop a music playing without the need of open the window. It’s unbelievably useful.

If you drag the title bar of the window to the top of the screen. The window's outline expands to fill the screen. To return the window to its original size, drag the title bar of the window away from the top of the screen.

Mouse option: Press "Windows logo button " + Up Arrow / Down Arrow to maximize/minimize the window.