I would say:
(1) Uninstall mega-pack (see
this post why.)
(2) Register and download latest BSPlayer from the
original site
(3) Install BSPlayer
(4) For starters install DivX-codec and perhaps XviD
See
this post and/or
this post.
For further codecs needed use
adicoto's list of codecs as also mentioned in the earlier posts referred to hereabove.