I have a New-to-Me Phillips DSR7000.  new original disc, version 6.4. Went though the guided set up, and first phone call and activiation, then I used MFStools to expand to a 750 drive.  Pulled and booted in the Tivo... all good.

 Ran the PTVNET with success on the 750gb drive, replaced to the Tivo, and it is in a reboot loop... 

I've checked the cables and pulled the power a couple of times, not luck.