Non-Routable IP conflicts

We are trying to deploy an Intranet company wide to disseminate project information. We do NOT provide internet access to users except IS dept and a select few other admin types. We provided them with a static non-routable IP (192.168.x.x). The problem is each machine now indicates a IP conflict on boot with a machine with MAC address 00:C0:7B:… This address is not in any lists of ethernet vendor addresses we can find. How do I resolve the conflict?