Just an FYI - If you're running a router that has a firewall built in (I don't know if they all do but Belkin does) and a firewall on your PC you shouldn't have any problems with the two. I think the issue comes in with two on the PC. You can test your "visibility" on the net by going here
http://www.hackerwatch.org/probe/. I've tried it on different PC's and different levels of security and it seems to work pretty well.