I don't have a good experience with that belkin router, that stands in the faq. But well, I don't like hardware routers with too much functions on them. My "stupid" nat router, only has to forward 5121 to have nwserver working normally, including posting the game on gamespy. Anyway, if you have a belkin router (maybe on others too), look for an option "Filter Internet NAT Redirection" and disable it, if your router has that option and if it's enabled, it may cause problems if you host something.
If you forwarded all the ports correctly, and it doesn't works. Then check on your server, if it's firewall isn't blocking it. (disable it completly and try to connect then, if that works it's the firewall) WinXP SP2 has a building firewall too, don't forget that one if you have WinXP SP2.
If you still think it's the router, most include an option to forward evry connection made to 1 host, like if the computer was directly connected. My router calls it DMZ.
A DMZ (DeMilitarized Zone) Host is a host without firewall protection. It allows a computer to be exposed to unrestricted 2-way communication for Internet games, video conferencing, Internet telephony, and other special applications. This function is typically used to allow a web server, FTP server, etc to be accessible to users on the Internet.
But your server may as well call it something else.
Used 10 time "if" in this post
(ok, now 11)
-Mel