Differentiating dummy adaptor from actual NIC

You could try a call to SetupDiGetDriverInfoDetail, if there is no HardwareID: http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q259695 (you will have to change the inner call).

If that fails (a false HardwareID) then see if the PCI bus location exists using SetupDiGetDeviceRegistryProperty and SPDRP_BUSNUMBER.

Hope this helps.

Couldn't get SetupDiGetDriverInfoDetail to work. It requires DeviceInfoData and DriverInfoData.
DeviceInfoData is retrieved from SetupDiEnumDeviceInfo().
Trying to get DriverInfoData from SetupDiEnumDriverInfo() which always returns error 257 (i.e. no more items) even with index 0.

Code snippet:
================================
for(i=0;SetupDiEnumDeviceInfo(hDevInfo,i,
      &DeviceInfoData);i++)
{
SetupDiEnumDriverInfo(hDevInfo,&DeviceInfoData,
      SPDIT_COMPATDRIVER ,i,
      &DriverInfoData);
SetupDiGetDriverInfoDetail(
      hDevInfo,
      &DeviceInfoData,
      &DriverInfoData,
      DriverInfoDetailData,
      buffersize,
      &buffersize);
=================================

Hmm, odd.  Did you try the SetupDiGetDeviceRegistryProperty?  That matches the code in the MS link exactly.  You just need to change the SPDRP_DEVICEDESC to SPDRP_BUSNUMBER.  You can also get the driver name to identify the driver, a physical device object name (which may be valid even if the device is virtual) and a bunch of other data on the device.  Here's Microsoft's list of properties: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/install/hh/install/di-rtns_a60fa017-1c15-45bf-a178-37516bc0aea1.xml.asp

Also, you could try using SetupDiGetSelectedDriver to get the DriverInfoData.  That should return the driver actually used for the device, rather than a list of compatible drivers.  Unfortunately this is a rather touchy area of the windows API, and much of what Microsoft says needs to be taken with a big grain of salt.  Short of experimentation, there's no way to be sure what is going to be returned.

It doesn't work. After changing SPDRP_DEVICEDESC to SPDRP_BUSNUMBER it doesn't put anything in buffer, just null.

1st 3 bytes of NIC MAC address are vendor code. Is there any standard using which vendors assign last 3 bytes? e.g. could they start with 00-00-00 and 00-00-01 and so on?
Could we just safely test last 3 byte values with some minimum value to verify whether it is actual NIC or wage?