ASF (Advanced Streaming Format) is a file format that stores audio and video information and is specially designed to run over networks like the Internet. It is a highly flexible and compressed format that contains streaming audio, video, slide shows, and synchronized events. ASF enables content to be delivered to you as a continuous flow of data with little wait time before playback begins.
WMV - Audio/Video Windows Media. Requires version 8+ of the Windows Media Player. Note: This file is also found as a video/audio file on the Xbox.