I've been using Win 8 Pro for a couple of months now, but a few days ago the metro interface stopped appearing, and I've been unable to get it back. I know a lot of people want it disabled, but I've gotten used to it, and in particular the WIN+I shortcuts for the menu....

The keyboard itself is still functional. I ran a check using OSK, and it shows that the system registers the key as being pressed, so it's not a physical fault on the keyboard.

The metro screen no longer opens when the WIN key is pressed, and the system panel doesn't open when the move is moved to the far right either...

I've had to resort to installing the "Win 8 Start Button" Application to get me the functionality that I need.

Is there some kind of quick key that disables it which I might have pressed by accident?

The only changes I can think of are having plugged in two USB hard drives which had some old data and were then formatted. FYI the virus scanner didn't alert me to any potential threat.... The change that I think is more likely is one of the auto updates from either Microsoft or the antivirus program (BitDefender 2013), but I can't remember which one performed last.

Any help greatly appreciated. Thanks.