Ok, I finally "got brave" and resolved to use MSTOOLS to upgrade (3) of my Premiere. The original (320GB to 4TB) worked fine. Then I got lazy and used the same SOURCE to copy to (2) 1TB HDs. But the (2) remaining Premieres refused to TRANSFER recordings no matter what hoops I and they jumped through. Wasted HOURS. Finally I did use MFSTOOLS on EACH original HD (which I had kept) to copy to EACH of the (2) 1TB HDs, and everything works. Somehow the Original HD contains critical information that is mated to that particular TiVo.