|renaming a file will not change it's format, nor will it miraculously make it work. |
You are correct in that it's a codec issue. By default, Windows will not play mov files, usually you need Quicktime or some other viewer that have the mov codecs for playback. You probably installed a codec pack at some point. Google "codec packs" and you will be presented with tons of them. Find one that has mov codecs and install it.