hi there....
K750i cannot plays MPEG4 video.
you should convert it into 3gp format..
as long as i knew it...
Actually, K750i CAN play MPEG-4 videos, that is, the phone supports
MPEG-4 codecs but only packed in 3GPP (*.3gp) container. You can use
any existing MPEG-4 codec (DivX, XviD, ffdshow MPEG-4) and wrap the
video inside 3gp container. Standard *.mp4 container is recognized as
an audio file (regardless of whether you have video inside, only audio
will be played, if audio codec is supported)... Hope that helps :)