Some other software installs can cause a conflict with Windows networking -- the most common I've found is the Bonjour DNS Responder. It is installed by ITunes and some Adobe products, and is generally not needed. Go into Services, stop the service called Bonjour and change it from automatic start to either disabled or manual start. Then restart computer.
If that doesn't work you can try going to the command prompt run as administrator and type ROUTE DELETE 0.0.0.0, should remove the phantom network, which is probably due to Bonjour anyway.