Summary: Mine died after a couple of years in my blu-ray player. I read on another review that there is a micro sd card inside, so I took mine apart. Sure enough there is a unbranded micro sd card inside. I tore apart the back looking for it, but it ended up sliding out from the front. If you look into the mouth of the USB drive, there is the gap on one side, the contacts in the middle layer and then the shiny black plastic is the micro sd card.
Summary: Nice small size but it takes forever to load it up with music. The little tether cord that it comes with is difficult to lace into the small holes (the cap keeper holes) Finally got it with a pair of tweezers and a safety pin. The packaging is a little odd. My roommate opened her package up with scissors and ended up cutting her tether in half, not knowing that it was hidden in the back of the package.
Summary: Very good when it's working, and one day... it DIES! WON'T even show up in my desktop or being detected at all. Can't fix it as of now, but trying hard to get it back to work. Truly a very portable drive; small & heck yea, 4GB, it's the BOMB!