The directory of file cannot be created on my mp3 why?

Try adding some detail -- like model name and number, is the player appearing in Windows as an external drive, is the player's memory almost full, does the player's setup screens offer options of appearing as a media player or as a drive when attached to computer ?

From comments I've found, this looks like another horrible SigmaTel derivative. Normally you could format the memory in Windows on SigmaTels, but there's a warning that you lose functionality on this model.

So look for an internal format facility among the player's setup screens-- you'll lose your music -- if pos first copy it to your hard disk (if it's not already there).