You do not need a server to do this. Windows Media Encoder will stream video directly from a Win XP Pro box. It also has a screen capture codec that compresses the full screen into less than 150 kilobits/second at 10 fps.
Tell Windows Media Encoder to use "Screen Capture" as the video device, and whatever audio device you want. On the Output tab, select "pull from encoder" and choose a port number that the clients will connect to. (They can use HTTP or MMS.) Then on the Compression
tab, choose Windows Media server (streaming) - Video: Screen Capture (CBR), then choose a bit rate & frame rate.