I really enjoy the thoroughness of the developers of K-Lite codec packs. They really do try to think of everything when creating a neat little tool to solve all of my problems when I want to watch a video. I'm not a technical person, so the principle of "click and get it" is, honestly, my salvation from being a complete noob. That's why I usually download and install K-Lite Mega Codec Pack of all the available versions.
K-Lite Mega Codec Pack, like all the versions of K-Lite packs, can effectively provide media playback of music and video files in most of the formats used on modern hardware, and even some used on the older machines. It is compatible with most major media players, but supports its own Media Player Classic provided along with the pack. It supports DirectShow filters, VFW/ACM codecs, and almost every other extension and format you need for playback, both of HD videos and older compressed ones, as well as both low-quality and uncompressed audio. The main difference the Mega Codec Pack has is that it supports video encoding (VFW) for MPEG-4 (Xvid), H.264 (x264VFW), Lagarith and Huffyuv. Audio encoding for MP3 and AC3 is available as well.
But, on the whole, the Mega version is not that different from the rest. And why would it be? K-Lite products are my favorite especially because they give so much without demanding a lot in return.