Play MKV Files in Windows 7

I've been using Windows 7 Media Center as my dedicated media hub for the last few weeks, and it's been a nice upgrade from Vista Media Center. Some improvements include support for up to 4 tuners for each type (QAM, ATSC, etc...), a lot of interface improvements, and HD support to name a few. It can even play AVI/DivX files natively without needing any add-ons.