SOLVED: windows 8 doesn't recognise a new installation of the arduino software

I have just purchased a tablet running windows 8. Loaded the present version or the arduino software and it runs fine.
I have connected a nano to the usb port and the nano has the blink programme in it that is flashing correctly.
The computer says I have connected an unrecognised device and fails to see the arduino.
The pulldown in the software has the port heading greyed out.

Have I downloaded the wrong software or have I missed something else you can see?
The leads and nano work fine on my old computer.
Thanks,
mat.

I have tried to update the drivers according to the getting started section but it says the most up to date drivers are installed.
The information in the reference section for getting started doesn't mention windows 8 but a readme file in the software I have downloaded says there is now a new all working driver and the old drivers are in a zip file?

The port section of the tools pull down is still grey and there is no port connected?

I have kept trying various things to get the drivers to work and I don't know how but the computer now recognises the board so everything is up and running.