You almost got it: $ eix -c w32 [N] dev-util/w32api (--): Free Win32 runtime and import library definitions $ eix -c win32 [N] media-libs/win32codecs ((~)20071007-r4): Windows 32-bit binary codecs for video and audio playback support
It's also a use flag for vlc and mplayer (that's for my setup, probably other players support it too), it will pull the package for you.
