There is such a thing as too many codec. If you have downloaded several codec packs you may have the same or similar codecs installed twice or even three times. This will often confuse the players.

Try downloading VLC player. It has built in codecs and will not use any other codecs www.videolan.org . If that plays your files then it's time to clean up your codecs and maybe players as well. Then start over. Media Player Classic is quite good and then just install the codecs as you need them and try to stay away from downloading more than one codec pack (or even none if you don't mind installing single codecs as you find the need)

Also .mov files (quicktime files) are very often currupt or turn out to be something quite different than what you intended to download. Usually turn out to be porn if they even work.