When you plug cable in do you see a Green Light with a blinking yellow light?
If you dont see a green light lit when cable is connected then try replacing the cable your using to see if this fixes the issue.
Does Device Manager show that all is correct for this Network Adapter or a Red or Yellow icon showing a problem or a warning that something isnt quite right?
If you enter CMD
at start RUN and hit enter and then enter IPCONFIG/ALL
does it show an IP address? If so is this address a 192.x.x.x address or a 169.x.x.x address.
If you see a 192.x.x.x address, what do you see if you enter PING www.google.com
.... does it show that it resolves with an IP Address for the Google server that your system is pinging or an error message that its unable to ping google.