win 7 claims existing internet connection but browsers do not browse

Hi, I used to be a windows user but switched over to ubuntu for some time now. So, im a bit rusty on windows knowledge. Anyway, a friend who has a windows 7 laptop and a windows vista desktop asked me to help him share his usb mobile broadband connection. I obliged but its been two days now and I have no idea what I am doing wrong but his desktop just cannot browse!

Now to what I did:

I right-clicked on the mobile broadband connection and clicked on the sharing tab. I selected the "share this connection" tab and proceeded to select the local area connection.

On the desktop, which runs vista, I set it to connect , get IP addresses automatically.

Now, the Network and Sharing center tells me that it is connected to the Internet. But the browsers are unable to browse.

I cannot rely on ping here because even on the laptop, whenever an address is pinged, the request times out but i can still browse on it.

When I run windows diagnostics, it tell me that it cannot communicate with and gives the ip address.

What could be wrong? How do I solve it? I am beginning to look foolish:(

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