Windows Media Encoder has a feature whereby you can publish streaming video of your screen via HTTP or MMS. You can use Screen Capture as a source and Pull from encoder as an output. You may have to fiddle with the compression options to get the right balance of quality and bandwidth. Use the Edit button for a custom compression set-up under the Compression tab -- especially to set the video size to be the same as the input. The frame rate can be really low -- 3fps doesn't look bad. Note that you will probably have to reduce screen resolution to 800x600, 16-bit colour to avoid a cryptic "not supported" error.
There is a nice "how to" article on the Microsoft site, Getting Started with Screen Capture Using Windows Media Encoder.
