What you do need to do, is update the dns address of your site (or whatever you are trying to host in your machine).
At the risk of getting flamed (this being an old thread), I will point out that
you missed the point that his ISP was using a NAT router and assigning
him a private LAN address. Therefore, the only way unsolicited traffic
could reach him from the net would be for that router to be configured
to allow it. It's the same as having a popular home style router. You have
to configure port forwarding on the router if you hope to have your
server reachable from outside.

BTW, you are right, it would have been nice to know if he ever solved
the problem (by getting a new ISP, LOL).