Zoomplayer includes an "Install center" which will automatically download a hand-picked selection of codecs and codec-versions that work well together and give you the best coverage.
It will also be able to update these without breaking anything if you rerun "Install center" at a later time. During the initial install it will also detect codecs already installed and only update those that need to for it all to work in harmony.
This is what I always use these days, it has never failed me. Installing random codec packs or some multi-mega-pack from other sources seems to easily end in a lot of hurt sooner or later...
...as Zoomplayer these days is commercial (free trial includes the "Install center" though) they have to have a near-perfect selection of codecs as I bet they have to support it as well? ^^
I have always used CCCP with no issues. It's one of the first things to be installed on a fresh copy of Windows. – Jared Harley – 2009-08-10T03:39:06.573
CCCP is very clean and only includes what's really necessary. If you're interested, here's a list of what it installs: http://www.cccp-project.net/wiki/index.php?title=Advanced_FAQ#Exactly_what_does_the_CCCP_install_and_why.3F
– Badaro – 2009-08-10T04:50:33.453