In it’s latest push to become the central hub for all your media, Microsoft has quietly announced support for both DivX and XviD codecs. DivX and XviD are both the same codec, but both developed separately; with only XviD supporting both.
It’s expected that they will released some new media extenders to complement these new formats.
Ironically, DivX started as a illegal codec; using a pirated version of Microsoft’s MPEG-4 Version 3 codec. It has now been rewritten and is now legit. XviD is the open source version, but coded differently. XviD is popular with video file sharing, as it compresses the video.