bought twinbreeze kit to add 2nd drive to a model 649 80hr DT. All the instructions I've read on weaknees, hinsdale, etc. say to remove the original drive from TiVo and reformat it using MFS along with the new 2nd drive. Why do I have to format/reimage the original drive? why can't I just prep the new 2nd drive for TiVo and add it into the unit with the original on the new dual-drive bracket? is it due to having to "marry" the pair of drives to work together? thanks.