Have you tried cloning the MAC address of the Computer into the router? With some cable providers you have to do that as it first sees the Computers MAC address and then when you put in the router, since it's a different MAC address, it will lock out the router. Most good routers have a place to clone the MAC address. You can get the computers MAC addy at a command prompt by typing ipconfig /all.
You will see the Machine address. Type that into the router where it says clone MAC address. You did not state which router you are using. Some I know what menu it's on. Hope this helps. Has with a few Comcast friends of mine. I have a friend on COX and I am sure we had to clone the MAC address when he got his new router.