From your description you've lost me... Perhaps if you take a picture of the cable/ports you need and post them in here we'd be able to help you better..
The newer modems (255's) do NOT have a USB port anymore, to use them on a USB port you need a USB ethernet dongle or just install a PCI ethernet card.
Kymmy
---------- Post added at 16:29 ---------- Previous post was at 16:28 ----------
LOL Rob, simple minds think alike
Kymmy