Grab Nokia PC Suite from www.nokia.co.uk - make sure you get the
latest version that's compatible with your 6680.
Then you need the usb cable (a DKU-2) or a bluetooth dongle to use
your 6680 as a modem.

Having said that when i used to use my 6630 as a modem on Three it
never worked until i found the 6630 modem in the XP Control Panel and
within it's properties set a modem connection string:

+CGATT=0;+CGDCONT=,,"three.co.uk"

I think (!) that PC Suite is meant to automatically install your
mobile as a modem and when you choose network it should set any
connection strings required - but as i'd originally used my 6630 on
Orange i couldn't get PC Suite to update it's settings to Three and
had to do so manually after spending ages on the internet finding the
required connection string.

Martin.