Look at Robin Walkers website
When you first register with NTL your cable modem
remembers the MAC ADDRESS of your LAN card. This is a 12 character unique address. After registering with NTL you cable modem will only work with the
PC that it was first connected to. If you are using
a router to share the internet then you have to clone into the router the MAC ADDRESS (which is sometimes called the PHYSICAL ADDRESS) contained on
the LAN card of the PC that was first connected to the cable modem. Look up the info on MAC address on
robin walkers website.