I recommend

I usually don't recommend software to others for whatever reasons you can think of, but this one is so damn good that I cannot help but...:-). I now use it exclusively for playing all of my media files (and it plays pretty much everything out of the box, you can forget about all the hassles trying to install proper decoders).

Free KMPlayer at
http://www.kmplayer.com/forums/index.php

If you download the zip archive, you can simply unzip it to a directory and use it directly (so it's what people green software). Of course you can use the installable version too.

There's a Chinese forum on the site too:
http://www.kmplayer.com/forums/forumdisplay.php?f=7