Just to clarify - you have 2 PC`s one XP and the other Win2000. You are on NTL Cable broadband with a cable modem (Thompson? Which model?) supplied by NTL. You also have a wireless router which appears to be ADSL. How am I doing?
Can you explain how they are physically (cable or wireless) connected together based on my interpretation of your problem because I can see a small problem combining two routers one cable and one ADSL. Not insurmountable I hope but I need to know makes and models as well.