10 or so years ago, my first .mp3 player (wasn't a DAP) was a D-Link, which was the same size as the original walkman, and it was Hard drive based and had an ~ 800MB capacity. It was horrible. It was firewire and when you deleted songs, certain sectors of the song would be un-deleted and show up in the middle of other current songs .
D-Link couldn't figure it out. It was a known problem for them.