DreamScene[LINK] is a little known extra in windows Vista which allows you to replace your desktop wallpaper with a video of your choice. The video plays on your desktop as if it were a wallpaper. It doesn’t seem to bog down the machine although I’m running it on a dual core AMD with 2GB of RAM.

A nice curiosity but I found it a bit repetitive for long viewing. Someone definitely put a lot of time into this but it seems destined to failure as I can’t imagine anyone ever leaving such a thing running on their machine for very long.