I have some drives that I want to use as backups (WD 1.5Tb SATA). If I format them internal (XP machine), I will then be asked to format them when placed in an external USB enclosure (plugging into XP and W7). If I format them in the usb enclosure, I am asked to format when I hook them up as internal. When the drives return to the environment (usb or internal) where first formatted they are recognized fine. Previous WD 1.5Tb SATA have not had an issue with this...they are accessable in both environments. These new drives are the same model, but are newer. Any ideas on what is going on?