greetings, I had the IDENTICAL issue with my Sony Walkman. All of my computers suddenly, and without warning, would no longer recognize the Walkman. After a frustrating effort, I finally figured out how to fix it. If you would like me to provide you with the fix, just email me, or reply to this post, and I will give it to you. It takes three clicks of the mouse and two seconds to fix. It is unbelievably easy. I can't believe even Sony Support hasn't figured this out yet. I ended up providing them with the answers too, when it was they who should have been giving me the explanation and the answer to how to fix this. By the way, this fix works with ALL portable devices (mp3 players), not just the Walkman.