Windows 7 only: The latest DivX tech preview adds support for MKV video files to Windows 7, so you can use them in Media centre, Media Player and even show thumbnails in Windows Explorer.
Windows 7 already includes native support for AVI/DivX files, but MKV files are quickly becoming the standard format for media files in HD — and while you can play them using everybody's favourite, VLC Player, you won't be able to use them in Media Center or stream to an extender device like the Xbox360, and the thumbnails will just show a generic icon. Installing the DivX Tech Preview enables MKV support, so the video files will work in any application that relies on Microsoft's native media support, and even adds hardware acceleration for video decoding (if your video card supports it). Readers should note that you can continue to use VLC to actually play the files, but install this to get thumbnails working.
Hit the link for the free download (free registration required), and make sure to check out the CyberNet News post for the full explanation, including some extra links for additional filters to make sure all of your media works.