On the pots router you need to set the static bridge parameters to forward ATM1-4 to a valid mac address (your xp box) on your local area network, then setup PAT to send traffic coming into your router on a particular port to a port on your xp box, sp2 on xp will require the opening of ports on your pc as well(security centre firewall) before you can send trafic to it.Also dont forget you will need to setup an account with a dynamic dns provider, and have a piece of software update the ip address to their database from your pc, there are lots to choose from, and plenty are evn free (the ip update software also)