AM
Not that I disagree, but I understood that would only be the case if you were running OSX Server. The ethernet switch acts as a bypass to the mac and therefore it's firewall on that port. I accept that I maybe wrong - it's not something I've ever had to try.
Binos
See
Networking with a Windows PC for more info on Windows file sharing. Also see
Setting up Windows File Sharing. It's in human speak. I believe all routers and indeed Airport also have firewall protection so it becomes a bit of a non-issue when you go down that route.
Trips