1.
CODECs list and alternate players for Movies; ie: user a program like GSpot to identify which codecs you need to play a particular file.
2. I'd recommend to get
VLC - (click on link) _ (choose nearest mirror site) as it has in-built codecs & is generally very reliable. See it's abilities here
http://www.videolan.org/vlc/features.html & is a good incomplete video file previewer!!!
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You can also downld extra skins for it.