I called TiVo and they can't figure it out yet either. I have an officially sanctioned WD 1TB My Book AV DVR Expander that was working for months on my TiVo HD (RCN leased). I have purchased a TiVo premiere elite and want to move this drive to the new box (I realize I will lose the recordings). I have tried every combination of steps including making sure the old TiVo boots up, recognizes the drive missing, and "unpairs"... But no matter what - the new TiVo recognizes the drive but then says it is unsupported. I read the model number to the TiVo support guys on the phone and they confirmed it should be supported and they don't know what is wrong. They also confirmed I have the latest software. This is really bumming me out and making me very worried about my Premiere Elite purchase - can somebody make a suggestion?