Re: MP4s
Personally I wouldn't use rewriteable CDs they are expensive and slow to write to - ordinary CDs are less 40c each - they are a cheap disposable item. I am surprised rewritable CDs are still available.
DVDs are actually better because they hold 5 times (?) more and cost about the same. You could even made a proper DVD (ie with a menu) out of your MP4s using a free program like
DVDStyler or even Freemake that can be played on any DVD system player.