I agree,  mpeg is definitely not the format of choice for your PPC,  you can
recompress to divx (avi) which gives great results but tends to be a bit
confusing, or you can use windows media encoder to convert to .wmv which
will play in the default media player, is very easy and straightforward to
configure and gives acceptable results versus file size..

I tend not to use MPEG's as I've found even with a tiny amount of
compression, the video still looks pretty pants. 300KBit/s was the worst
quality compaired to 300Kbit/s DivX video.

Use PocketMVP and encode your videos into DivX. Free codec, free app to
compress the files with (VirtualDub)

Plus if you HAVE any MPEG's - PocketMVP will play them too.