Dreamscene

Tried out a Vista Ultimate extra last night called "Dreamscene". It plays (in a loop) any mpeg or wmv file as your background wallpaper. Nice idea in principle, but using it on my 3Ghz P4HT laptop with 1.2Gb of RAM, it was very resource hungry and the video noticably juddered when doing such things as opening an application or moving a file.
Besides, it really does nothing more than rip off Nvidia's NVDVD which was released in November 2002 (yes, 5 years ago !) and plays dvd video as the desktop wallpaper - and from what I recall, Nvidia's application was a lot less resource-hungry, running perfectly happily on an Athlon 2Ghz with 512Mb RAM !
Still, it is only in the preview stages, so hopefully Microsoft will iron out the stuff that hogs the system resources before going officially live with it - and hopefully, they will allow you to use .avi files as well as mpegs and wmvs since these are the most widely used types of video files these days - despite Microsoft pushing their wmv format !