Power everything off, including the Cable Modem, which must be left without power for five minutes
This is IMPORTANT so that it loses the association between the existing connection
(recognised by its MAC address) and the IP address that it has allocated to it.
After 5 minutes power on the Cable Modem and, when fully booted with all lights displayed, power on the Router.
When the router is fully up and running, power on the PC.
The Cable Modem will recognize a new connection and allocate a different IP address to the router
The router will allocate an IP address to the computer