I assume that you have Win7 Home and cannot apply the simple solution of :
Administrative Tools / Local Security Policy / Network List Manager Policies, double-click your network, tab Network location, and set its type to Private.
For Home, use this thread which is for Vista but will probably work for Win7:
Vista Network Identification for Loopback Adpater.
As registry changes are required, I advice to create first a system restore point.
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.
