Windows DreamScene is a utility that allows videos and other optimized animations to be used as desktop wallpapers.

One of the purported advantages of DreamScene over previous methods of desktop animation is that it makes use of the GPU for display instead of the CPU, leaving the latter free to perform user tasks. To what extent this is achieved is not specified. Content encoders need to strive for a balance between compression and file size; decompression requires the CPU, but larger files take up more memory and may cause the disk to be accessed more frequently.

source. wikipedia

Dreamscene on squidoo.