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How do I reformat an unmountable/unrecognised/unformatted USB drive? It will not mount or format on Windows Vista or OSX Tiger.

  • Disk Utility sees the hardware, but no partition to mount.
  • Testdisk does not see it at all.
  • USB Probe gives me the info:

    SM3252A Memory Bar, but externally it is a 4GB HP memory stick

  • fdisk dev/disk2 gives me:

    /dev/disk2 is not a character device or a regular file

  • & fdisk dev/rdisk2 gives me:

    Disk: /dev/rdisk2       geometry: 0/4/63 [0 sectors]
    Signature: 0x0
             Starting       Ending
     #: id  cyl  HD sec -  cyl  HD sec [     start -       size]
     1: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
     2: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
     3: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
     4: 00    0   0   0 -    0   0   0 [         0 -          0] unused      

I'd prefer to do this on OS X or the Unix shell, but any suggestions for a solution on Vista would be welcome too, or Linux for that matter.

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If Disk Utility sees it can't you create a partition and format it from there, or try the same with gparted? – Dennis Oct 5 '11 at 19:10
Might check out parted,, command line *nix partition utility. – jmreicha Oct 5 '11 at 19:16
I don't understand the point. You can buy a new one for under $10. – Daniel R Hicks Oct 5 '11 at 19:52
Are you sure /dev/disk2 is the name of your usb device? What is the output of fdisk -l – Prahlad Yeri Mar 2 '13 at 14:37
i have recovered a LOT a nearly-going-to-the-trash-can flash drives using gparted on linux, simply by destroying the partition tables and rewritting them and then formatting. is this an applicable solution? – Lorenzo Von Matterhorn Apr 4 '13 at 2:16

Not sure, but can dd command be of any help?

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in Windows Vista or higher, you can try to format it with diskpart.

Open a cmd.exe with administrative privileges and type "diskpart".

The command "lis dis" lists all your storage devices. If your USB stick is on the list (e.g. device number 3), you can select it with "sel dis 3".

Then you can reformat it with "clean", "create partition primary" and "format fs=fat32 quick".

For additional information see

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