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I have a 150GB USB external hard drive (IDE/Parallel ATA disk in an enclosure) which was formatted as one partition, FAT32 in Windows XP. I wanted to extract the files off of it using my Macbook Pro running Apple Macintosh Leopard (Mac OS X 10.5.6).

However, when I plug it in, I get a dialog box which says:

Disk Insertion
The disk you inserted was not readable by this computer.
Initialize…   Ignore   Eject

I saw many references to there being a 127GB or 128GB partition limit for FAT32 for Mac to successfully mount.

Also, a potential problem was that when using Disk Utility it shows up on my system incorrectly as formatted as a Windows NT Filesystem (NTFS-3G).

diskutil list disk3

Output:

/dev/disk3
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:     FDisk_partition_scheme                        *149.1 Gi   disk3
1:               Windows_NTFS                         149.0 Gi   disk3s1

It did however mount automatically and show up when I was running a virtual machine, for example Parallels and Windows XP (I used VirtualBox and Windows 7), but copying over files this way proved to be very slow.

So, after spending a lot of time on the internet looking for solutions, I just tried mounting it from the Terminal (command line) with success!

First, make a mount point:

sudo mkdir /Volumes/EXT_HD

Now mount (your device numbers may be different, e.g. /dev/disk2s1 — you can determine what it is as it will the the highest number when you issue the command ‘ls /dev/disk*’):

sudo mount -t msdos /dev/disk3s1 /Volumes/EXT_HD/

It eventually showed up in Devices in Finder, but just to let you know, when I tried ejecting (unmounting) it when I was done, even though I had closed all programs I got the error:

The disk “USB_DRIVE” is in use and could not be ejected. Try quitting applications and try again.

Unmounting via he command line also failed:

sudo umount /Volumes/EXT_HD/
umount: unmount(/Volumes/EXT_HD): Resource busy

So I had to reboot.

I hope someone finds this information useful because I sure didn’t find any help…

EDIT (01 Oct, 2009): Apparently there is a way to enable native NTFS read/write support in 10.6 Snow Leopard (and this may work for Leopard). However, I would recommend not allowing write ability (and thus read only) when using this method as it may corrupt your NTFS files. To set to read only, follow the directions in the link but instead of using ‘rw’, use ‘ro’, e.g. UUID=123-456-789 none ntfs ro