Has the Windows 7 machine been able to connect in the past?
I suggest reinstalling the network card drivers. Right-click on the device in Device Manager, and select Uninstall. Reboot, and let Windows automatically install the latest drivers. Be sure you are hard-wired into the router first, if possible.
I have a problem when I shut down my PC the "Internet" Ligh in the Modem turn On, this happens when a screensaver appear so when I go back i can't open any page unless I disconnect/connect the DSL again and the"Internet" Light still OFF.