The file extension MWV is used by windows media video files. “WMV” stands for “window media video. This is an alternative format to compete with the RealPlayer multimedia format. This is very helpful and can also be used for many different quality levels of multimedia such as; high quality video presentation, lower-resolution streaming and ultra-high quality high definition television. file extension MWV is a compressed video file format for several proprietary codecs developed by Microsoft . If this is what you need, go to their website for more information. To download is absolutely free with their very easy instructions. Get it before your files crashes!