How can I check ethernet card? I doubt a hardware problem with my ethernet device. I'm unable to connect to Internet. How can I verify if it's a hardware issue or not?
If you have access to a second computer, connect it to the same ethernet cable and port.  If that computer gets internet access (be sure to disable wireless, so you know it's connecting via ethernet), the first computer's ethernet device is faulty.  If the second computer does not get internet access, try swapping the ethernet cable for another (the first could be badly crimped or faulty in other ways), and try another ethernet port.