Can you please be a bit clearer as to what you have. From what you have said, I gather that you have adsl broadband through a Netgear adsl router. Is this connected by a wire (an ethernet cable) to your pc (the XP64 one)?
Secondly, to set up a wireless network, your XP64 pc will need a wireless pci card inside it or a wireless USB adapter connected to it. Do you have one or the other?
Thirdly, you are right in saying that your son's pc will also need a wireless pci card or USB adapter. Does his pc have USB ports?
It sounds as though you will need one or, more likely, two wireless adapters of some kind.