When ever you need to switch between open windows in Windows XP or 7 you need to press Alt+Tab.It will work on both windows XP and 7. But now in Windows 7, this feature has a little Difference
Never heard about Aero Flip 3D. It is the new feature in Windows 7.This feature is used to switch between open windows. just click Windows Key + Tab.To use Aero Flip 3D, Press and hold the Windows button along with the tab key,holding the windows button press the tab key to move the Flip 3D. This will move the windows in a Sequence and you can see all your windows in sequence. Once you see the window that you want to open, release the windows and Tab buttons. This will open the selected window
The behavior of the Windows Key + Tab key is same as the Alt + Tab key but the only difference is how the open windows appear on your screen.