Windows Media Encoder Handy for Compressing to WMV. Even though this compression tool has been around for a while it’s free and might prove helpful for compressing .AVI files to .WMV files. With Windows Media Encoder you can do a custom encode of source files for the compression. The encoding time will be based on how long your video files are. Creating .WMV files could be really useful if you’d like to import videos into a PowerPoint presentation.