I like Media Player Classic. Been using it for years, but for sure, there are some types of media files that it will not play.
But the simple solution is to download and install the "K-Lite Codecs pack".
That's all that Media Player lacks, the codecs necessary to play some of the newer media types.
Once you get the K-Lite Codecs, they will offer you updates every few months, just to keep it up to date.
Needless to say, I always accept the updates. It's one of the few updates that I DO accept.
It's one of the first things I install on a new Install of Windows.
The K-Lite Codec Pack is a free software bundle for high quality playback of all your music and video files. It is easy to use, but also very flexible with many options. Enjoy problem free playback of MKV, MP4, AVI, FLV, and all other multimedia file formats.
codecguide.com
Cheers Mate,
Shadow