That I had on my stolen laptop that told me what codecs were needed to play a particular file and whether I had a suitable one on my system - any idea what it's called - I can't play mp4 files although I've downloaded mp4 codecs galore!
you could use a codec like DivX, XviD or even Nerocodec these i am pretty sure should let you play back mp4 files, but also you need a player compatible with the codecs, i suppose the easiest is in fact windows media player because many codecs are actualy made around compatibility with this program because every user of their codec would have it...
I believe a splitter is what splits the different data streams. For example, you might have a DivX video stream with an MP3 audio stream muxed together in an AVI container. Other containers like Matroska MKV allow for subtitles and othe streams, even though they may also use DivX video, and MP3 audio. You need special software to deal with the MKV container, since it's not built into Windows like AVI support is. MP4 I believe also uses a container not included with Windows. Windows won't know how to deal with the data in your MP4 container without some extra software.
