Networking 2 PCs with public IPs through ZoneAlarm

Hi,

I am running ZoneAlarm Pro 3.7 on my PC, which connects to the Internet through a cable modem.  I have another computer which also connects to the Internet through this cable modem, and both computers are connected to a switch, and are assigned public IP addresses.  When I first ran Zone Alarm, it gave me a dialogue about a new network it had found.  I checked the IP address and it was the Internet connection for computer 1.  I wanted to check if it would update the IP address field if I renewed the IP address, but it did not.  Does this matter, or will it still be keeping me safe from the Internet anyway?

My other question is this: there a safe way to network the computers considering they both have dynamic public IP addresses?  I did have them networked (which only worked after installing the NetBIOS and IPX/SPX protocols on both computers (both running Windows XP Pro)), and was not alerted to any danger until I received an advertising message using the net messenger (the one accessed by running 'net send' from the command prompt).  Is there a way to add the computers to each other's trusted sites, or run the network over NetBIOS or IPX/SPX so it cannot be accessed by other people?  I did consider adding their subnets as trusted, but after reading on some site, concluded that was not a good idea.

Should I invest in a router/2nd network cards for each computer, or is there a more practical solution, for example require a specific username/password combination to access network resources?  If this is possible, is it possible to make it standard so these settings are applied to all future folders which are shared?

If anyone has any ideas how to do this, can they please give me instructions both for doing this and for setting up ZoneAlarm to allow the 2 computers to be networked.

Thanks in advance.

sneakysnake