What you do is, you use WinMFS to go onto the 1TB drive, which will put 160GB worth of partitions on there, and then you use WinMFS to expand into the rest of the drive by adding an MFS pair of partitions. Then you use mfsinfo (part of WinMFS) to make sure that you have used all of the drive, and that there isn't any space left over at the end. If there is, it will be considered an Apple Free partition by the Apple Partition Map scheme of doing things, and it'll interfere in the next step. If all went well, WinMFS will have put 13 partitions on the drive, and then added two more. This lets you add 1 more before breaking the "only 16 partitions per drive" TiVo rule. That's where jmfs comes in. jmfs copies the 1TB to the 2TB, and then adds a single MFS partition, taking up the rest of the space. If there were extra space on the 1TB (which got labeled an Apple Free partition), that would have been copied over by jmfs along with everything else, which would have made it the 16th partition, and the MFS partition added by jmfs would have been the 17th partition, and the TiVo would have thought it was a malfunctioning external drive and insisted on divorcing it, leaving you with only the first 1TB useable on that 2TB.