Formatting External Drives for Windows and Mac Usage

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Before undertaking the task of preparing a drive for "native" use by both Mac OS X and Windows, make SURE any data you want to keep is backed up. The formatting procedure outlined here IS DESTRUCTIVE and cannot be easily undone. That said, the steps are:

  • Decide how many partitions you will need. Normally, this will be a choice between 2 or 3.
    • If 2 are used, one will be Mac OS Extended and the other NTFS.
    • If 3 are used, one will be Mac OS Extended, one NTFS, and the third FAT32.
    • If all systems involved are new enough to support ExFAT (FAT64), then this should be used instead of FAT32.
  • Format the disk partition table in Disk Utility. Make sure to use Master Boot Record if you'll be using the disk with Windows XP or earlier Windows versions, as your partition scheme. It is safe to use GPT (GUID Partition Table) if the disk is larger than 2 TB and/or will only be used with Windows Vista or newer.
  • Select the file system for each partition. Format the NTFS partition, which MUST be the first one on the disk for Windows to recognize it, as FAT32 for now.
  • Unmount the disk from your Mac, and connect it to Windows.
  • In Windows, open Computer Management from Administrative Tools in Control Panel, then Storage.
  • Select the partition you formatted as FAT32 earlier - it'll be the first one on the disk.
  • Format it as NTFS this time. Leave the options at their defaults.
  • Unmount the disk from Windows, and connect it to the Mac, to make sure it recognizes all partitions on the disk (which it should).

If everything works at this point, you are done!