if you're on about frontrow as in the mac feature all you need is for quicktime to have the various codecs,
as frontrow uses quicktime to as its player. so if quicktime can play it, it can play in frontrow
flip4mac is useful and free now, thanks to m$ cancelling devel on the atrocious windows media for mac,
as well as divx i'd recommend the xvid-delegate and ac3 codecs to play stuff through frontrow