slartibartslow

I have a NW-HD1 which I have used satisfactorily for years. I have recently needed to reformat the HD on my computer, which naturally deleted SS & My Library. No worries, I thought, I can re-import them to My Library & keep them there as my NW-HD1 back-up. On re-importing, I discovered that although the tracks were shown in My Library complete with full information, what they were only seemed to be links to the tracks on the NW-HD1, and could not be played. Worse still, the import process seems to have corrupted all the music on the NW-HD1, so that I get the error message "CANNOT PLAY TRACK ERROR". This applies to all tracks on the NW-HD1. However, they are still there & playable, as I can play them through my PC using SS. In short, I have lost the usability of my entire music collection. Can anyone advise how I can recover the situation?