My MP3 player, the one I bought a couple of years as a present was a Sony nwd-810SF model, and both my wife and I thought the sound quality was excellent. However, the buttons on the Unit started to malfunction after a year or two, so I upgraded the BIOS thinking that was the problem. This only made things WORSE! The unit used to restart itself continually until the batteries ran out.
I rebooted the entire unit several times and several different ways, all to no avail. It’s now difficult for me to recommend any Sony model MP3 players at all, because of my experience with this one. If you’re looking for an MP3 player, you would do well to consider other models than the Sony model. If you really would prefer, buy a good quality mobile phone and make sure the in-built MP3 player offers acceptable playback quality.
Surprised? Yes, I was by the poor quality. The only thing I can use it for now is a USB drive (woops! Even that doesn’t work). I’m just trying for the fourth time to see if I can’t boot it back to life. Otherwise it’s going out in the electronic recycle garbage. Perhaps it’s not a shock to see the stock for this company in the doldrums, after all.