About recent problems with hosting servers on Windows XP:
What you can try, in case you only forwarded specific ports and you did not try DMZ:
Get following tool:
http://www.nirsoft.net/utils/cports.html
(Scroll down for download link)
Start ServerLauncher.exe and create an Internet server with port e.g. 11001
Start CurrPorts and then forward all port which are used by HD2.
Now restart the server and see if it works.
That way i was at least able to add the server on
nomandown.com/hd2/servers/
If you create a dedicated server and want to join it on the same machine you need to connect with your local address (e.g. 192.168.178.23:11001)