mp3 player questions

[cold_cash]

Hey all.

My sister is considering buying a Dell mp3 player, and since both she and I are both pretty ignorant about them I figured I would turn to you for help.

My main question is this: Can you use your mp3 player as a portable hard drive for storing misc. files, much like you would use one of those "thumbstick" drives?

Do all mp3 players have this capability, or is it available only on some? (Or none, if the answer is 'no'.) If the answer is 'yes', this would kick ass, IMO.

I heard something about iPod batteries and how they sucked and blah, blah, blah, so we were exploring some alternatives. I don't think she wants to spend more than $250 though, so the choices may be limited. If you have any recommendations on the tip of your tongue please feel free to share them.

Thanks.