The RPC Endpoint Mapper Client Authentication machine setting should be configured correctly. Enabling this setting directs RPC Clients that need to communicate with the Endpoint Mapper Service to authenticate as long as the RPC call for which the endpoint needs to be resolved has authentication information. Disabling this setting will cause RPC Clients that need to communicate with the Endpoint Mapper Service to not authenticate. The Endpoint Mapper Service on machines running Windows NT4 (all service packs) cannot process authentication information supplied in this manner. This means that enabling this setting on a client machine will prevent that client from communicating with a Windows NT4 server using RPC if endpoint resolution is needed. By default, RPC Clients will not use authentication to communicate with the RPC Server Endpoint Mapper Service when asking for the endpoint of a server. Fix: (1) GPO: Computer Configuration\Administrative Templates\System\Remote Procedure Call\RPC Endpoint Mapper Client Authentication (2) KEY: HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Rpc\EnableAuthEpResolution