A list of
CODECs sources can be found here: 1.
Free-Codecs.com, 2.
Nimo’s codec pack, 3.
CoDecs & codec identifiers, 4.
K-Litecode Codec Pack
Also get a backup player with built-in codecs such as
VLC:
http://www.videolan.org/vlc/ (choose nearest mirror site)
Take my word for it, it's worth having around!