Laptop Won't Connect To Internet Wirelessly or Wired

I can't access the internet with one of my laptops. I have two other laptops and they can access the internet. So I'm certain the issue is with the laptop . . . not with router, modem, etc. When I search for wireless networks the laptop locates the router signal and, in fact, says signal "strong." When I click connect, however, it does not connect. So I got out my Ethernet wire. And I connected it directly to the router. I still can't access the internet! What should I do?