Windows media services / Netshow

I am experiencing difficulties broadcasting a powerpoint 2000 presentation. I wish to broadcast only over a workgroup LAN to between 20 and 30 clients. No video or audio requirements. Win2000 Server with media services installed and a Win2000 file server, no AD installed.
When I attempt to broadcast the presentation I receive error message-“Failed to connect to netshow encoder.” when i click details it reads”audio capture source requested was not installed”