TiVo Community Forum Archive 1 (http://archive.tivocommunity.com/tivo-vb/index.php)
- TiVo Upgrade Center (http://archive.tivocommunity.com/tivo-vb/forumdisplay.php?forumid=25)
-- Which Drive Is Best... (http://archive.tivocommunity.com/tivo-vb/showthread.php?threadid=164266)

i'm no expert either, but have migrated several Tivo's to larger drives. I think you maybe in luck in moving a single 160GB to two 120GB disks if you dont do an disk image copy. It may take longer than a straight 'dd' + add the 2nd disk.