7 has a firewall built in. It also blocks things depending on whether it thinks you are on a Public network or not.

Unfortunately, there are so many variations on this theme that it's hard to tell what you can do to fix it.

Check:
Start -> Control Panel -> Network and Sharing Center. If it says "Public" then you'll likely have no internet access.

Start -> Control Panel -> Administrative Tools -> Event Viewer and browse through the various Windows Logs and similar things in the left panel. Maybe it'll give you an indication of the errors and what is causing it.

Can you browse sites using the IP addresses in the browser address bar? I assume not, but that might be another thing worth checking.

E.g. http://74.125.228.20 is www.google.com (here, anyway)

Good luck.

Cheers,
Scott.