I've tried three times to reply to this - hope it workd this time. Your post suggests you still have the connection via the USB on the 98 machine. The idea of the router would be to route the connection to both machines. My setup is to connect the cable modem to the router and then connect the router to both machines. This can be by cable (needs a network card) or via wireless cards (I fitted a wireless card into my desktop).
If you keep the connection on one machine you set up the router as a Wireless Access Point (mine has this option) and use ICS. This means the PC with the connection needs to be on to connect and rather defeats the idea of a router. I think there can be problems between 98 and XP with this setup.
The only ISP setting you need on the router interface is to set the host name as 'ntlworld' - I had to guess this bit. Good luck. With more details I might be able to make more suggestions