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How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac

This wikiHow teaches you how to fix an 'External Hard Drive Not Detected' error on your computer. There are a number of issues that can cause an external hard drive to not be detected. It could be a simple issue with the cord, USB port, or...
Method 1 of 6:

Basic Troubleshooting on Windows and Mac

  1. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 1How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 1
    Check the USB port. There are a numbers of ways to check to see if a USB port is working. Look inside the port to see if there is any debris or obstructions. Make sure that USB connections are snug and do not wiggle. Try plugging the external hard drive into a different USB port to see if it works on a different port. Plug a different device into the USB port to see if it works with other devices.
  2. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 2How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 2
    Check the USB cord. If you determine that the USB port is working properly, check to see if the cord is working properly. See if the USB cord is able to power a different device. Try swapping the cord with a different one.
  3. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 3How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 3
    Check that the drive is receiving power (if possible). Most external hard drives and some USB flash drives have external LED lights on them. Check to see if the lights are lighting up to see if the lights are lighting up.
Method 2 of 6:

Troubleshooting with the Device Manager on Windows

  1. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 4How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 4
    Right-click on the Windows Start
    How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 5How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 5
    button. It's in the lower-left corner of the task bar. Right-clicking the start menu displays a list of different managers you can use to troubleshoot problems on your computer.
  2. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 6How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 6
    Click Device Manager. This opens the Device Manager program on your computer.
  3. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 7How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 7
    Click Other Devices. This displays a list of assorted devices on your computer, including unrecognized devices.
  4. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 8How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 8
    Right-click Unknown device. If there are devices on your PC that don't have the proper drivers installed, they appear as "Unknown devices" in the Device Manager.[1]
  5. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 9How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 9
    Click Disable. This displays a prompt asking if you want to disable the device. Click Yes to disable the device.
  6. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 10How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 10
    Right-click Unknown device again. This displays the pop-up menu.
  7. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 11How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 11
    Click Scan for hardware changes. It's near the bottom of the pop-up menu. This scans for new devices on your PC.
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    Right-click Unknown device again. This displays the pop-up menu.
  9. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 13How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 13
    Click Enable. It's the second option at the bottom of the pop-up menu. This re-enables the device.
  10. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 14How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 14
    Right-click Unknown device again. This displays the pop-up menu.
  11. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 15How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 15
    Click Update Software Driver. It's first option in the pop-up menu.
  12. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 16How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 16
    Click Search automatically for updated driver software. This searches for the latest driver for the device online.
  13. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 17How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 17
    Click Universal Serial Bus controller. This displays the all the USB ports on your PC.
  14. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 18How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 18
    Right-click the USB port(s). This displays a pop-up menu for the USB port.
  15. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 19How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 19
    Click Properties. It's at the bottom of the pop-up menu for the USB port.
  16. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 20How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 20
    Click the Power Management tab. It's the last tab at the top of the Properties menu.
  17. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 21How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 21
    Uncheck
    How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 22How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 22
    "Allow this computer to turn off this device to save power". Repeat for all USB ports on your computer.
Method 3 of 6:

Troubleshooting with Disk Management on Windows

  1. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 23How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 23
    Right-click the Windows Start button. It's the button in the lower-left corner of the task bar. Right-clicking the Start button displays a list of managers you can use to troubleshoot issues on your computer.
  2. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 24How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 24
    Click Disk Management. This opens the Disk Management program on your computer.
  3. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 25How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 25
    Right-click the external hard drive (if displayed). If the external hard drive is displayed in Disk Management, right-click it to display a pop-up window.
  4. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 26How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 26
    Click Change Drive Letter and Paths. This displays a box that allows you to change the drive letter for the device.
  5. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 27How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 27
    Click Change. This allows you to change the drive letter.
  6. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 28How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 28
    Select a new drive letter and click Ok. Use the drop-down menu next to "Assign the following drive letter" to select a new drive letter for the external hard drive. Click Ok when you are finished. Changing the drive letter may force Windows to recognize the hard drive.
  7. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 29How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 29
    Right-click any unallocated space. If there is any unallocated space on the hard drive, it needs to be initialized in order to be recognized by Windows.
  8. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 30How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 30
    Click Initialize Disk. This opens a window that allows you to initialize the Disk.
  9. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 31How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 31
    Click Ok. This initializes the disk so that it is recognized by Windows.
    1. By default, the disk will be initialized as a "MBR (Master Boot Record)". If the external hard drive is larger than 2 terabytes, select "GPT (GUIT Partition Table}.[2]
  10. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 32How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 32
    Format the drive. If the external hard drive was formatted on another computer platform, such as Mac or Linux, it may not be recognized by Windows. If all else fails, you can reformat the drive for Windows. If you plan on using the external hard drive only on Windows, select NTFS as the file system. If you plan on using it with other devices, select FAT32 as the file system. Warning: Formatting the external hard drive will permanently erase all the data on the external hard drive. Use this step as a last resort. If possible, try to backup any files you want to keep to another computer. Use the following steps to format the hard drive.
    1. Right-click the external hard drive in Disk Management.
    2. Click Format.
    3. Type a name for the drive.
    4. Select NTFS or FAT32 next to "File System".
    5. Click Ok.
Method 4 of 6:

Showing External Drives In the Finder on Mac

  1. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 33How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 33
    Open the Finder
    How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 34How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 34
    . The Finder is the blue and white icon with a smiley face. It's in the dock at the bottom of the screen. If an external hard drive is not showing up in the Finder, it could be that External disks are not checked in the preferences menu.
  2. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 35How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 35
    Click Finder. It's in the menu bar at the top of the screen on the left next to the Apple icon. This displays a drop-down menu.
  3. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 36How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 36
    Click Preferences…. It's the second option in the "Finder" menu. This displays the preferences menu.
  4. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 37How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 37
    Click the General tab. It's the first icon at the top of the preferences menu. It has an icon that resembles a light switch.
  5. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 38How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 38
    Click the checkbox
    How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 39How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 39
    next to "External disks". If the box next to "External disks" is not checked, external hard drives will not be displayed in the Finder. Check this box to make sure you have access to external hard drives in the finder.
    1. You may also want to check "Hard disks", "CDs", "DVDs", and "iPods", and "Connected servers" to make sure you have access to all devices in the Finder.
Method 5 of 6:

Resetting the SMC and VRAM on Mac

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    Reset the SMC. SMC stands for System Management Controller. Sometimes resetting the SMC can resolve USB and other issues on Mac. The way you reset the SMC is different depending on what type of Mac you have. Read "How to Reset the System Management Controller (SMC) on a Mac" to learn how to reset the SMC. [3]
  2. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 41How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 41
    Reset the NVRAM. If resetting the SMC doesn't fix the issue, you could try resetting the NVRAM. To reset the NVRAM, simply reboot your Mac, and press ⌘ Command+⌥ Option+R+P until you hear a chime. Read "How To Reset NVRAM on a Mac" to learn more.
Method 6 of 6:

Troubleshooting Using Disk Utility on Mac

  1. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 42How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 42
    Open the Finder
    How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 43How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 43
    . The Finder has a blue and white icon with a smiley face. It's located in the dock at the bottom of the screen.
  2. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 44How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 44
    Click Applications. It's in the side bar to the left. This displays all the applications installed on your Mac.
  3. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 45How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 45
    Click Utilities. It's the blue folder in the Applications. This displays all the utility programs for your Mac.
  4. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 46How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 46
    Click the external hard drive volume. It's listed below the drive name in the sidebar to the left. This displays how much of the external hard drive has been used.
  5. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 47How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 47
    Click Mount (if available). This button is at the top of the Disk Utility app. This forces Mac OS to read the external hard drive. If the button says "Unmount", the external hard drive is already mounted. If the "Mount" button is grey out, Mac cannot read the disk.
  6. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 48How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 48
    Click First Aid. If there is no volume for the external hard drive, or the mount button is greyed out, Mac cannot access the external hard drive. Click "First Aid" at the top to scan the external hard drive for errors.
  7. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 49How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 49
    Click Run. It's in the prompt that appears when you click "First Aid". This runs a scan of the external hard drive and attempts to fix any errors.
  8. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 50How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 50
    Click Repair Disk. If First Aid finds errors on the external hard drive, it display a list of the errors and ask if you want to repair the external hard drive. Click Repair Disk to fix the errors on the external hard drive. If First Aid is unable to repair the external hard drive, it may be formatted in a file system that MacOS can't read, or it may be a faulty external hard drive.[4]
  9. How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 51How to Fix an 'External Hard Drive Not Detected' Error on PC or Mac Picture 51
    Click Partition or Erase. If the external drive has be formatted using a file system that can't be read by MacOS, you could either partition the unused portion of the external hard drive, or erase the entire drive and reformat it in a file system that can be read by MacOS. If you plan on only using the the external hard drive, select Mac OS Extended as the file system. If you plan on using the external hard drive on other devices, select FAT32, or exFAT as the file system. Warning: Erasing and reformatting your external hard drive will erase all the contents on your external hard drive. Use that as a last resort. If possible, try to back up the contents of the external hard drive to another computer before reformatting it. Use the following steps to partition or erase your external hard drive:
    1. Partition:
      1. Click Partition in Disk Utility.
      2. Type a name for the partition next to "Name:.
      3. Select a format for the partition next to "Format:".
      4. Type how much space you want to allocate to the partition next to "Size:".
      5. Click Apply.
    2. Erase:
      1. Click Erase in Disk Utility
      2. Type a name for the external hard drive next to "Name:"
      3. Select a file system next to "Format:"
      4. Click Erase
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