USB Wireless adapter says there is internet connection, but cannot access internet?

[Vegas Matt]

A friend of mine has a Netgear USB wireless adapter on their desktop (running Windows XP). The Netgear software says there is a connection to the internet (via her wireless router), and the icon in the bottom right of the screen says there is an internet connection, but when she tries to run Explorer or anything else using the internet, it says there is no connection.

Anyone know what the problem could be? Is there a good website that could help me with this problem?
"Turn off DHCP, type your DNS server addresses in manually, try again. "

I have no idea what this means.
Also, the modem works fine. There is another computer connected (not wirelessly) and it works fine.

[Trevor]

You need your internet drivers.

[MASTERUDY]

YES FIRST IT ALL MOST LIKELY IS THAT THE ROUTER IS A G B N ETC AND THE ADAPTER IS NOT COMPATIBLE ANOTHER THING IS THAT IS NOT CONECTED PROPERLY THE SECURITY KEY WAS NOT INPUT RIGHT YOUR BEST BET IS GET A CYSCO LINKSYS ADAPTER AND THAT ONE COMES WITH MULTIPLE SETTINGS AND WILL WORK FINE

[cen]

Turn off DHCP, type your DNS server addresses in manually, try again.

If it still doesn't work, check if you have an Internet connection at all by pinging some numerical IP. If it fails, you have no Internet connection. Try connecting directly to the modem and pinging some numerical IP again. If it works, your problem is the router. If it still doesn't work, your problem is either your modem or it's something beyond your control at your ISP.