You never did say what brand & model your router is. That could be important for us to know.

You shouldn't have both XP & Norton firewalls runnng together. They are known to conflict with each other. Giving you less security not more. And may also give LW problems. I'd suggest disabling XP firewall, & reconfiguring Norton firewall. (a) Reconfiguring Norton Firewall, & (b) Configuring Norton Internet Security

Did you mean you are running your router in DMZ mode. It's not safe to run it without any security or you risk cyber attack via ddos attack or hacking into your computer.

My guess is that after reinstalling your OS, your computer ip has changed & thus your router isn't relating to any port forwarding or UPnP. If you're running on a lan or shared internet connection then this is probably what's happened. You should reset your internet settings. And also configure your router by telnetting into it & enabling UPnP or else, port forwarding: http://portforward.com/routers.htm