Android HTC HD2 is using hardware keys for home, back and menu function. These hardware keys might have issue if using them too much (luckily mine still okay). So we have Button Savior which is sidebar style software keys. And now another Android application called zMooth comes to save your HTC HD2 hardware buttons. It uses gestures to mimic back, home and menu hardware keys. By the way, zMooth requires a rooted android device.