It's wise to only run one firewall b/c 2 may interfere with each other. So if you're running McAfee firewall then it's best to disable XP's firewall. See: http://www.limewire.com/english/content/firewalls.shtml

Do this simple test for us. Using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?

Hopefully your Belkin router utilises UPnP technology. If not you may be best to forward a port for LW. If you do need to do this then you can find instructions here: http://www.portforward.com/routers.htm
The process involves 1. Setting up a Static ip (most important for this to work.) 2. Forward port 6346. 3. Within LW: Manual port forward instructions & sample image & 2 posts after that.

Tell us how you go.