Presumo que você tenha o Win7 Home e não possa aplicar a solução simples de:
Ferramentas Administrativas / Diretivas de Diretiva de Segurança Local / Diretivas do Gerenciador de Listas de Rede, clique duas vezes na sua rede, na guia Localização da rede e defina seu tipo como Particular.
Para o Home, use este tópico que é para o Vista, mas provavelmente funcionará para o Win7:
Identificação de Rede do Vista para o Adaptador de Loopback .
Como as alterações no registro são necessárias, aconselho a criar primeiro um ponto de restauração do sistema.
If you make the following modification to the registry, Vista will ignore your adapter in the Network and Sharing Center and always consider that adapter on a private network.
Open regedit and navigate to the key
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class{4D36E972-E325-11CE-BFC1-08002BE10318}There will be multiple keys with similar names, the key is that the default value on this one should read 'Network Adapters'.
Under that key there will be a bunch of subkeys (depending on how many network adapters you have installed) and they will be four digit numbers, such as 0008. So you have to find the key that corresponds to the network adapter you want to modify; use the DriverDesc value to help you identify it.
Once you have found the key, add a DWORD value to the key called "*NdisDeviceType" with a DWORD value of 1. Note: common mistake is to leave off the asterisk, which should be included as part of the value name.
For more information on the values for this setting, check here.
Essentially you are setting the device to be an endpoint mapper which causes Vista to ignore it but still leaves it functional as a network device.
Usually you have to disable and then enable the network adapter in the Network Connections control panel in order for this to take effect. In some cases you may also need to reboot.