Hi,
the Iriver firmware uses a different format (XviD) for the videos. You can either boot to the original firmware to watch the videos or convert them to mpeg2 so rockbox can play them.
See also:
http://www.rockbox.org/twiki/bin/view/Main/WebHome?topic=PluginMpegplayerBy the way, this is not an installation question. And please don't write your whole post in bold letters.