there are different issues in your setup that could be causing the problem, have you checked the xp link and the networking links/info in the first post on this thread?
You could try typing /localinfo -u to see if that will grab the external ip for the machine you are on.
I know all this stuff can be confusing. Dont forget, you can go into #mIRC on the network you use or on one of the other networks and ask one of the ops for one on one help.