Given that the Windows ICF can hamper file sharing (I know; ironic isn't it?!) you should kill it off forthwith. Either using no firewall or, if your nervous, use Kerio (which I have found, after much experimentation, to be about the most networkable firewall available. And it has a free version).
That'll be a good start.
Step two; learn to network with Norton Firewall (and good luck with that; it can be done, as another forum member found recently with some hard work, but it's not as easy as it should be).
Also, remember that when a firewall blocks or limits functionality in a workgroup, it's not actaully a bad thing. It's designed to do that and it's then up to you to fine tune the network permissions to suit your needs.
For example, my network consists of my office PC and laptop, plus my wife's laptop and the family PC. I have used the firewall settings to create one-way access between my PCs and the other PCs; my PCs see each other's shares freely, but the family PCs cannot see my shares even though I can see theirs.