Sorry to hear about double trouble with your units. The Tivo identity is in a chip on the motherboard. You can always change the hard drive without changing the Tivo identity (see the Upgrade Forum). My understanding from reading this forum is that even though the Tivo identity stays the same when you change the hard drive, that the cablecard relationship will still need to be updated by the cable company.I have 2 Tivo HD units. 1 has blown out one of its tuners we'll call it Tivo "A". The other has a failed hard drive we'll call it Tivo "B". What I have decided to do is take the hard drive from the Tivo "A" and replace the hard drive in Tivo "B" resulting in 1 working Tivo. I'm sure this will result in a call to TWC to come out with a new cable card. I'm curious as to what identity the hard drive swap will make Tivo "B" assume. I guess the question is what determines the identity of a Tivo the software or the hardware?