Although it is for a completely different discussion, many people in the digital media segment online are strongly against codec packs, as am I. The reason being is that there are several codecs that have cross-compatibility which are often installed by said codec packs. This multi-format support for different codecs causes several overlaps, and can quickly lead to incompatibilities and playback issues. One such thing would be divx/xvid files, which are supported by ffmpeg, xvid, divx, and likely a whole host of other codecs because of their popularity. Installing one may not fully override another and you'd be left with a mash-up of things that can lead to an overall poor experience. Personally, I'd only recommend installing codecs as needed and only installing them from the original source. So if you need to play quicktime files, install Quicktime from Apple, real codec files, install real media, etc. Overall, I've found that the major codecs are supported in Vista, the only one that isn't is x264 wrapped in the *.mkv container. The only other that isn't that I try to avoid is Quicktime for streaming media, but I doubt one really needs more than possibly 3-4 codecs installed to play 99.9% of the digital files out there.