Ignore the FAT, indeed ignore the Windows MBR and its contents. They aren't the problem. You can use fdisk (or Disk Manager or whatever) to set them up correctly over MSC -- if the Carbon is offering the correct size partition to MSC in the first place. That is the part set up by the first, proprietary, partition table, which is all you really need to fix.

One worrying thing that's just occurred to me, though, is that the Carbon has a 24-bit CPU. 2^24 512-byte sectors is -- 8GB. There might be a worse problem here than we thought.

Peter