"Is there Windows/GUI-based cloning software I can use?" I do not know. I fear most of them would be looking for some sort of DOS type partition structure (or might even try to create one) Perhaps WinMFS, select the Seagate, then click on mfscopy, then select the WD as the target. At least it understands TiVo drives. How did you get all 2TB of the Seagate expanded into?