Well, that's reassuring then. The native MP3 thing is really my only major beef with the NW-MS70D. Otherwise, the beautiful design (it's basically a MD remote with an extra lump on it) and materials make it nicer than your average cheapie MP3 player.
If I had the ability, investigation of those DAT and playlist files with a hex editor might yield some info. That way we could make it show up in the playlist. That makes the assumption if fed the MP3 data, the hardware can play it back.
But I don't know, there could be something more--like a specially placed configuration file, or some sort of binary firmware in the right directory. Maybe the unit has the hardware for MP3 playback, but needs some sort of firmware to be loaded first.
Or, maybe not at all. There's also the possibility we're reading far into the words of some random marketing guy, who absent mindedly said "And we'll offer this on older units too!". And that leaves the MemoryStick walkmans as what they are, which is an MD player minus the MD transport and with a virtual flashdisk added.
Calum