I've now tried installing the Linux Internet Gateway Device upnpd daemon on sol.

No UPnP shows up on my Win XP machine, even after reboot of the XP machine.

The problem is that the web page that the UPnP server exposes (on the style of http://172.16.1.11:49152/gatedesc.xml) is firewalled on the linux box.

Why doesn't the IGD/libupnp manage to add firewall rules to let packets through?

This page seems to have some possible solutions: http://gentoo-wiki.com/HOWTO_Setup_UPnP_with_IPTables