My problem now is that I want to have a firewall on the host computer (other than windows xp built in one) but as soon as I activate one the client pc loses connectivity (internet connectivity...lan works fine). I first tried with zonealarm pro 5.5 (latest build) and I had the settings enabled on the host for a gateway. I added the subnet mask, ip address of the client (even tried with an ip range) and the local net connection in the advanced tab of zonelarm as trusted zone. After trying the best I could and even checking all the help zonelarm site had to offer all I could get was skype connecting which was an improvement, but browsers and msn messenger cant connect. I even tried opening ports reducing the security of the trusted zone to zero and internet zone to medium and still nothing. The client also has zonealarm pro and the feature of forwarding messages to the client firewall works:P.
Having given up hope with ZA I tried other firewalls: Kerio, sygate, bullguard..etc but although all seem to have an option for setting the host as a gateway, their default settings are not good for it to work.
One more thing, the host pc had norton internet security initially(set to auto configure security settings) and with it ICS worked. After formatting the pc I wanted to install a different firewall cause I just dont like norton's IS...too heavy for the pc! Also on the various firewalls i used i didnt let them autoconfigure allows and blocks because I like to know which apps I let and which I dont. If someone could please answer this post at least so I can choose a proper firewall and set it up for ICS.Thanks.