Xvid is not a video format. Since Xvid uses MPEG-4 Advanced Simple Profile (ASP) compression, any video that is encoded with it is termed "MPEG-4 ASP video" - not "Xvid video" - and can therefore be decoded with all MPEG-4 ASP compliant decoders. This includes a large number of media players and decoders.
Xvid encoded files written to a CD or DVD can be played in a DivX compatible DVD player.