To use MSMQ as an RPC transport on computers running Windows NT, you must install Windows NT Service Pack 3 on each computer that will send or receive RPC packets over MSMQ. To use MSMQ as an RPC transport on computers running Windows 95, you must install DCOM 95 on each computer that will send or receive RPC packets over MSMQ.
MSMQ servers (PEC, PSCs, BSCs, and MSMQ routing servers) forwarding MSMQ messages that encapsulate RPC packets need not be running Service Pack 3. However, it is recommended that you install Service Pack 3 on all MSMQ servers if you are going to be using the MSMQ RPC transport.