Find IP Address/Location of Person Using Anonymous IP Servic

We have a simple message board that is being ruined by a few posters that are using anonymous IP services to hide their address and location. We have a record of the approximate time and the "fake" IP addresses which are generated by a service in some cases. We are seeking a method to identify the actual IP address and physical location of the posters so that they can either be blocked, notified of inappropriate behavior or legal action taken.