networking and the internet

I have 2 pcs connected together and know they are communicating because i am able to access documents on pc2 through pc1. The problem is the internet... pc1 connects directly to the internet through a webstar cable modem, and pc2 connets to the internet via pc1 (or at least thats what its supposed to do). But when i try and access the internet on pc2 i get "The page cannot be displayed", and when i try and sign into msn messenger on pc2 it wont connect so i run the msn trouble shooter and get the message "The troubleshooter has determined that you may not have internet connectivity". How can i sort this? ive tried to run the network wizard a few times and its obviously working because of being able to access the documents on pc2 through pc1, but the internet just wont work.
Hope someone can help.
Thanks in advance.
Nicky

 

ive just disabled Zone Alarm and pc2 will connect to the internet, so the problem obviously lies within the configuration of zone alarm. any ideas?