TiVo.Net – Turn your TiVo into a media center for your video files
TiVo.Net runs as a Windows service that serves your video files (in their various formats) to your TiVo as a if it were a TiVo GoBack server.
It’s early for the software, so expect bugs and quality issues. Oh and you have to compile the code yourself (unless you can find it compiled out on the net somewhere).