Have a look at these instructions for Norton.
PortForward.com - Free Help Setting up Your Router or Firewall
http://www.gnutellaforums.com/226610-post6.html

Make sure that the Windows firewall is turned off

If you're still stuck, please post your details. The thread below refers to LW but it's the same for FW!
System details - help us to help you (click here)