I recently “hacked” my TivoHD by copying the internal drive to a larger capacity drive. The larger space is useful, but better yet, I now have the original drive as a backup just in case the one in the Tivo dies. (My old Series 1 Tivo lost a couple of drives over the years.)
There is plenty of information out there on how to do this upgrade, and I am far from expert on it myself, so I won’t go into details except to say that I used WinMFS running on a Mac Pro. The two SATA drives (the one from the Tivo and the new one) were mounted internally.
Which is where I ran into difficulty. WinMFS (running in WinXP under VMWare Fusion) did not recognize the two drives. I even tried booting MFSLive in an Ubuntu VM, but again, no drives. I googled the problem, but the workaround appeared to be to buy a couple of SATA->USB adaptors for the drives.
Eventually I hit upon the obvious (in retrospect) solution, which was to boot directly to Windows using Boot Camp. WinMFS worked like a charm in that configuration.
If someone is aware of a way to get WinMFS or MFSLive to recognize internally mounted Tivo drives under VMWare Fusion, let me know. Otherwise, Mac Pro users should go with adaptors or with Boot Camp.