Windows 7 has added support for most multimedia file types straight out of
the box, unfortunately leaving out Matroska. DivX has stepped up however,
and has added Matroska/MKV support to the latest beta of DivX 7. This means
that Windows will be able to play MKV files properly, including the ability
to automatically transcode and stream these files to the Playstation 3 and
XBOX 360.
http://www.hardcoreware.net/mkv-windows-7-xbox-360-ps3/

Thanks!