Windows Key + What it does

Windows key 

 Display or hide the Windows 7 Start menu (same as clicking the Start
button on the Windows taskbar)
Windows key +Pause/Break Open the System Control Panel window
Windows key +D Toggle between displaying the Windows 7 desktop by hiding all open
windows and then redisplaying all minimized windows (same as clicking
the Show Desktop button on the Windows taskbar)
Windows key +M Minimize all open windows on the desktop
Windows key +Shift+M Redisplay all minimized windows on the desktop
Windows key +E Open Computer in an Explorer window
Windows key +F Open Search Results in an Explorer window
Windows key +L Lock the computer or switch users
Windows key +R Open the Run dialog box
Windows key +T Cycle through programs open on the Windows taskbar
Windows key +Tab Cycle through open windows in Flip 3-D
Ctrl+Windows key +Tab Enable you to cycle through open windows in Flip 3-D using your
arrow keys
Windows key +spacebar Preview the desktop by making all open windows transparent except for
their outlines
Windows key +U Open the Ease of Access Center Control Panel window
Windows key +X Open the Windows Mobility Center
Windows key +[number key] Open the window attached to the Quick Launch button on the taskbar corresponding
to the number you press, so that when you press Windows key +1,
Windows opens the Internet Explorer window because Internet Explorer is
the first Quick Launch button (to the immediate right of the Start button)
and pressing Windows key +2 opens the Libraries Window Explorer window because
the Windows Explorer button is the second Quick Launch button on the
Windows 7 taskbar