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USB External Troubleshooter


There are several reasons why an external hard drive may not be accessible or detected when you connect it to your computer.

While it is possible that your external hard drive may have come with bundled software that may be incompatible with newer operating systems, this is typically just ‘back up’ software, and the drive is not dependent on that software to function.
The external hard drive itself, under normal circumstances, should be detected by your operating system, without the need of drivers, software, or firmware updates.

If your external hard drive is not accessible please try these basic troubleshooting steps first.


Basic hardware troubleshooting steps:

  • Try connecting the drive to a different port on the computer.
  • If possible, try using a different cable.
  • Try using the drive on a different computer.
  • Verify the drive light is on. Desktop Drives typically require a power adapter. No light could indicate the power adapter is not connected to power.
  • Try a different power outlet. (Desktop Drives)
  • If using a surge protector or power strip, plug the power adapter directly into the wall outlet instead.(Desktop Drives)

For advanced troubleshooting steps select your operating system:





Check both Device Manager and Disk Management in the Computer Management console:


  • On your keyboard, hold the Windows Key () down and press R.
  • Type compmgmt.msc into to the run box.
  • Click on Device Manager on the left.
  • First check the Disk Drives section in the middle window by double-clicking it.
  • Look for your drive name. If you see the drive is detected here continue reading. If not, click here.
  • Right click on your external drive listed under Disk Drives.
  • Click on Properties.
  • Click on the “Volumes” tab.
  • Click on Populate.
  • Document the disk number provided in this window (Disk 1, Disk 2, etc…).
  • Now click on Disk Management on the left hand side. This will allow us to view the drive’s health.
  • In the middle towards the bottom locate the disk number from earlier.

Once you have located the drive you will want to look for the following:

Does it show RAW or Unallocated? Either of these indicates a possible issue with the drive’s formatting.

If the drive shows as RAW or Unallocated and you have already tried a different port, cable, and computer but you need the data, then you will want to consider data recovery.
If you do not need any data from the drive, you should be able to reformat the drive to restore accessibility. Read our How To Format Your Drive article for instructions on the process. WARNING: Formatting erases all data on the drive.


If the drive is formatted correctly for Windows you should see the following information:

  • NTFS - If NTFS is missing then the file system has become corrupted. You can format the drive if you don’t need the data.
  • Capacity - Check to see if the drive is correct, for example if you have a 1TB drive it should say 931GB.
  • Drive letter - Verify that the drive has a drive letter. If it is missing, verify that other drives have a letter. If other drives have a letter but the external is missing then you can right-click and select change drive letter or path.
  • Click Add then assign a letter and OK.




Drive not detected troubleshooting:

If the drive was not detected under Disk Drives then check the following:

  • Within Device Manager look for any entries called unknown device, other device, or mass storage device with a yellow ! icon. Important - Make sure to expand the Universal Serial Bus controllers section so you can see entries there as well.
  • If you see an unknown device or other device then right-click on it and select properties.
  • Under the general tab locate ‘Device Status’ and there may be an error code.
  • You may see a code 10 or 28.

If you see Code 10 and have already tried another cable and computer then the drive has probably failed.
If you need the data on the drive, then you will want to consider data recovery.
If you do not need the data and the drive is still within warranty, you will want to have the drive replaced. Visit the Warranty and Replacements section on for further details.

If you see Code 28 (this may work for others codes too, ie Code 43) then try the following:

  • Close the window with the code.
  • Right-click on the device with the issue and select uninstall.
  • Shut the computer down and disconnect the drive.
  • Reboot with the drive disconnected.
  • Once the computer is booted, plug the drive into a different port.
  • You should see that Windows is installing device drivers.
  • Once the driver loads, check to see if it is giving the same Code.

Note: If that fails, you will need to try to reload the USB drivers for the operating system by inserting your Windows Media, rebooting, and attempting a Repair/Restore.

Warning: This can be dangerous to your data and you should disconnect your external drive before attempting this.



If the drive is not showing on your desktop or within Finder check Disk Utility.

Open Finder > Applications > Utilities > Disk Utility

If the drive is not detected in Disk Utility then see the System Information/System Profiler section.

If you are using macOS 10.13 or higher then click view in the upper left and select “Show All Devices” which allows you to see both the disk as well as volumes.

The non-indented entry is the physical disk entry and when selected should say media in the name. In Mac OS X version 10.6 to 10.10 this entry will display the capacity of the drive instead of saying media. The indented entries will vary depending on how the drive is formatted but these entries will be volumes or containers associated to the physical disk.

Select the indented entry for your drive and click on the “Mount” button at the top of the Disk Utility. If the drive didn’t mount this indicates some level of file system corruption.

Select the indented entry and then click on First Aid

  • In Mac OS X version 10.6 to 10.10, click Verify Disk to see if the volume needs to be repaired.
  • Once the Verify Disk process is complete it will suggest you repair the disk or tell you there is nothing wrong with it.
  • If this is not the only copy of your important data, then try to run the Repair Disk process to see if it resolves the file system corruption.
  • If this is the only copy of your important data, then we suggest running data recovery software on the drive in an attempt to retrieve your files.
  • If the Repair Disk process fails to repair the disk then you will want to reformat it to see if you are dealing with a physical issue or a logical issue. WARNING: Formatting erases all data on the drive.
  • If there is no indented entry then the drive needs to be formatted or run the data recovery software on the drive in an attempt to retrieve your files.

If the drive needs to be formatted then click on the article that matches the operating system.
How to format a drive in Mac OS 10.6 to 10.10
How to format your drive in macOS 10.11 and above


If the drive is not detected in Disk Utility then check System Information/System Profiler.

Hold the Option key then click on the Apple Icon, the first entry should say System Information/System Profiler. If it says About this Mac then press and hold the option key again.

Once in System Information/System Profiler:

  • On the left-hand side locate Hardware
  • Under hardware locate the interface you are using (i.e. USB, Firewire, Thunderbolt, etc.)
  • In the middle window, locate the drive and select it
  • You should see the drive information listed in center at the bottom
  • The serial and/or model number should be listed

If the drive is not in System Information/System Profiler or in Disk Utility then try another Mac to see if the drive is detected there. If the drive is detected on the other Mac then continue with the following Apple specific troubleshooting.


Trying some of Apple specific troubleshooting may help resolve the issue.

Reboot into Safe Mode and see if the drive is detected. If it is detected then reboot back into normal mode and see if the drive is now detected

Apple Safe Mode -


If that does not resolve the issue then try each of the following resets. Sometimes it helps to do these more than once.

Apple NVRAM reset -

Apple SMC reset -



If you have exhausted either of the Windows or Macintosh advanced troubleshooting steps, and your external hard drive is still not accessible or detected, for further assistance contact Seagate support.