Many thanks for your reply. I have just now installed the Intellipoint software from Microsoft and that has seemingly updated the Mouse dialogue box under the Devices and Printers option in Windows 7 Start menu.
I now get the options you mention and the dropdown showing what you want the middle wheel click to do - trouble is there is no option for pan!! There is everything else but not pan. So I have had to set it to 'middle click'. I have also set it up so that it is 'application specific' for AutoCAD but STILL no luck when AutoCAD is open - it zooms in and out when you turn the wheel but nothing at all happens when you press the wheel. Grrrr!
I have literally spent months trying to resolve this issue and still no luck! So many variables - Windows version, type of mouse, drivers
installed, settings in AutoCAD etc. make it almost impossible to sort this out.
I lose the will to live with computers sometimes, great though they are....