Apologies for not replying before. I installed Windows 8 Pro but not (knowingly) the AMD driver. Automatic screen rotate worked. But after a week or so I didn't need that function, and when I wanted to use it again just a few days ago it had stopped working. I then reinstalled the device driver, plus the AMD driver - which Windows thought had already been installed. There was a moment of excitement when the screen changed from landscape to portrait, but there it stuck. I re-set it to landscape using Control Panel/Display. There I noticed that Windows 8 doesn't give an option for variable orientation: it wants you to tell it either portrait or landscape. So it seems I can change the orientation manually but not automatically.
Our friend and comrade IronFly has reached his 10,000th post to our little Community. During the last 4 years he has helped countless Acer customers providing help, advice and answers. The Acer Community team feels honored to count you as our friend. Thanks IronFly!