Your existing Network Card (NIC) must remain as the connection to your cable service and cannot be used in a double role.
You will need one further NIC in each machine, and this will provide the home network capability. The machines should be joined with a "crossover" cable, thereby negating the requirement for a hub. However, if you think you might want to expand the network in the future, a better option would be to use a router and then the whole concept needs to be re-thought out.
You will be able to access the internet via both machines, once the network is operating properly and you have successfully implemented Internet Connection Sharing (ICS). It is important to get the network operational, before trying to share the internet.