2 Wire is their combo modem/router unit from SBC Yahoo, I believe.  The desktop can connect either wired or wireless as can the notebook.

http://www.practicallynetworked.com/howto/
http://www.theeldergeek.com/quick_guide_to_simple_file_sharing.htm

On any computer running Windows XP with SP1, disable the Windows XP firewall. It will not allow File and Printer Sharing. On computers running Windows XP with SP2, make sure that the Windows XP firewall has File and Printer Sharing checked off on the Exceptions tab. If you are running any third party firewalls, like those provided by such programs as Zone Alarm, Norton Internet Security, or McAfee Security Suite, make sure they are configured to allow local network traffic