Inspiron duo 1090

hi there

I have an inspiron duo 1090 which I way it did when I cannot seem to make work the way it did when I first got it. I did a full reinstall of the operating system (Windows 7 Home prem) when I first got it and spun the screen it used to go into a tablet mode, but since the reinstall it doesn't do this. What have I forgotten to install please to make it do this as it was kinds cool looking?

Betty