First, make sure all of the required drivers are installed and up-to-date, and then go into the DOS prompt and use the ping command. Type "ping google.com" and if it gives you a reply you should be in business. This can help in diagnosing the problem in that if you do recieve a reply, you know automatically that the problem resides on a software level. If you do not recieve a response at all, you may need to check your hardware or it may be a problem with your ISP.