Mike, I don't think you need to worry about the computer. You stated that "Connect the lan cable from computer to the modem, and I have Internet." That right there would indicate, to me, that the computer is working correctly and the router has failed. It happens.. I've had 3 go over a 17-18 year span.
You could try holding the reset button in on the router for an extended period of time, (20 count) and then release it, but I don't think it will help in this case.
Sometimes I wonder whether the world is being run by smart people who are putting us on
or by imbeciles who really mean it.