You need to figure out what it is and install the correct driver. If everything is listed OK under network Devices it isn't your Realtek NIC. What's not working? It could be your onboard sound, card reader, etc. In Device Manager go to the properties for that device. Then go to the Details Tab and under "Property" select hardware ids. If you Goggle one of the lines listed for that it should lead you to what it is. Once you sort out what it is you can install the driver for it.