The vast majority of workstations here are Windows 7+, which means WMP will play h.264-encoded videos OOTB. Unfortunately, though, there are still some XP machines kicking around. (I believe they're due to be replaced sometime in the next year.) We need them to be able to play h.264-encoded video, preferably without having to install a third-party media player.
I know ffdshow can provide this capability. Perhaps other things can as well. I believe it's easiest for us to deploy something in MSI or MSU form. (We typically use CounterACT to push stuff like this.)