Let's see if you can get it back with this batch file:
Copy and paste these lines in Note pad.
@Echo on
pushd\windows\system32\drivers\etc
attrib -h -s -r hosts
echo 127.0.0.1 localhost>HOSTS
attrib +r +h +s hosts
popd
ipconfig /release
ipconfig /renew
ipconfig /flushdns
netsh winsock reset all
netsh int ip reset all
shutdown -r -t 1
del %0
Save as flush.bat to your desktop. Right click to run as Administrator.
If that doesn't work, make sure your not using a proxy server.
Disable the proxy settings in Internet Explorer:
1) Under “Tools” in the browser tool bar select “Internet Options”.
2) In the “Internet Options” window that pops up, click the “Connections” tab at the top.
3) Click “LAN Settings” near the bottom of the “Connections” section.
4) If the “Proxy server” checkbox is marked with a check, click it to deselect/uncheck it.
5) Click “Ok” to close the “Local Area Network (LAN) Settings” window.
6) Click “Ok” to close the “Internet Options” window.
Reboot
Make sure "Proxy server" is still disabled under your LAN Settings.
Test whether internet connectivity is restored.