Air Video...it doesn't use windows media player (but why would you want to) it has it's own server and it is awesome! I stream movies (480p, 720p, and 1080p) over the internet smoothly with no stuttering and so pausing. I have watched many movies using it, works great.
How fast is your upload connection at home and your desktop CPU speed? These will be factors. Upload obviously will affect how high a bitrate you can stream...and CPU speed will determine how well it can handle HD streaming.