try practicallynetworked.com

The short answer to your sharing
problem is to simply spend the
$50 or so on a home router and
plug everything into it.

The router will handle the
distribution of IP addresses
and security.

The only 'issue' is if your
cable setup requires you to
give the hardware/MAC address
of the connected computer to
the cable company. Even then,
alll you would need to do is
call the cable company and give
them the MAC address of the router
or get a router that can 'clone'
MAC addresses (most can).