The Matroska Media container is a very popular, open standard Multimedia container which is usually found as .MKV files. It is a very popular format in enthusiast circles and can be played directly in Windows Media Player with suitable codecs installed. We use the Combined Community Codec Pack (CCCP).
We ripped our BluRay disc of Sniper Reloaded to 1080P MKV and use Windows Media Player to playback the file.
MKV playback is demanding, although the system handles the task fine, with plenty of cycles left over for multitasking.