I really, really hope you didn't hook the TiVo drive up to a Windows PC and then booted the PC into Windows. If you did, you just corrupted the drive and it will no longer work in the TiVo. Windows will grab any drive it sees when it books and write to it, and when it does it breaks the TiVo formatting. Which can also make it not show up as expected in MFSTools. At that point, yeah, you may as well re-image it with InstantCake.