Mac data Lost When Re-Partitioning An External Hard Drive In Windows

by on December 17, 2007

Q: I have an external hard drive that I’ve been using as my back up on my OS X (10.4.11) Mac. I also own a PC. I tried to plug the hard drive into the PC and add an extended partition to save some files from the PC. I never saw anything about re-formatting or deleting the files that were already on it when I was adding the extended partition. But when I was done a minute later, the drive appeared to be wiped clean! None of the Mac files are there anymore. Do you suppose I can recover them?

A: While is may be possible to recover some of your data with software such as Disk Warrior, I doubt it. You say that the data, which was lost, were backups. Hopefully the original data are still on your Mac. If so, you can follow the advice in this answer to re-backup your data — this time is a PC compatible way. As you may be aware, Mac OS X and Microsoft Windows use different file formats. Macs use HFS+ while Windows-based computers use either NTFS or FAT. Traditionally, Macs are a lot more concerned with being PC compatible than Windows-based PCs are with being Mac compatible. This is true when creating disk partitions too. Macs can create and access FAT hard drive partitions. Windows on the other hand is not able to create or read HFS+ partitions. To be fair, I am not familiar with a method for creating NTFS partitions in OS X but FAT should work rather well on both Macs and Windows-based PCs. Please consider the following, which I have learned from a lot of trial-and-error over the years:

  1. Use a program that ships with OS X called Disk Utility on your Mac to create partitions on your external hard drive. You can create an MS-DOS (FAT) partition, which will work on both your Mac and Windows PC.
  2. You can have an HFS+ partition and a FAT partition on the same hard drive. However, Windows will not be able to recognize the HFS+ part of the hard drive.
  3. DO NOT attempt to create or modify partitions on your external hard drive via Windows. As you have already witnessed, this will corrupt the data on your external hard drive.
  4. Due to the way in which OS X manages FAT hard drive partitions, you may see some strange files/folders in your external hard drive when it is connected to your Windows computer. Do not worry. That is normal behavior.

I hope that I have managed to give you some useful advice. Good luck!