You shouldn't manually specify the IP, DNS, etc.
The router should be set to obtain an IP & DNS automatically - this is usually the default option.
The PC's network card should (to make it easier) be set to obtain an IP & DNS automatically. It will receive these from the router's DHCP server (which should be turned on - normally by default).
The STB needs to be rebooted. Then, you need to register the MAC address of the router -
http://homepage.ntlworld.com/robin.d...r.html#pacereg