First, I would try to ping loopback 127.0.0.1 verify if working, if yes then try to ping another machine locally on your lan ip, if this works then your adapter is fine..
Next, try pinging an actual IP address outside of lan (2 below)--not name, if you can ping the ip addresses that then your DNS is the issue--make certain have setup correctly--
the ip address for google is 64.233.167.991 or yahoo is 206.190.60.37.
If you can't ping those, then you should check to make certain if you can ping to your isp gateway... Have you tried this? If you can ping their gateway but nothing else you will need to call them for assistance.
Hope this helps