By Emily / Last Updated May 5, 2023

Help! My external HDD suddenly became “unallocated”

"Help me! I have my Seagate external hard disk drive 500GB and it is full of files and movies. It was working perfectly well yesterday. However, today suddenly became an “unallocated” drive without even a drive name. I'm able to detect the drive in the Disk Management but I have no way of accessing it. Any one can share some effective solution to hard disk unallocated repair? Thanks in advance!"-Extracted from sevenforums

Why is the hard disk unallocated?

Are you facing the same issue? When trying to use the drives, it shows as unallocated suddenly for no reason. Consequently, the data are there, but you cannot access them. Before attempting to fix it, we need to figure out what makes a hard disk showing unallocated first. There are many reasons that can cause this issue and they include:

1. Infection with a virus or spyware

2. Removing the hard disk improperly

3. Hard driver is outdated

4. Hard drive internal error

5. File system error

5 Ways to repair unallocated hard disk in Windows 11/10/8/7

According to the possible reasons for which the hard disk shows an unallocated listed above, here we offer a detailed guide to help you with hard disk unallocated repair in Windows 11/10/8/7. Before that, you can download and run the anti-virus software to clean up possible viruses in PC and external hard drive. If lucky, the problem will get fixed. If not, you can check out the following technical methods.

Way 1. Update the hard driver via Device Manager

1. Get to Device Manager by clicking on "Start" and typing in "devmgmt.msc" or by going to Control Panel and clicking on "Device Manager".

2. Right-click on the target disk under Disk drive, click on "Properties", then the Driver tab and then click "Update Driver".

Update Disk Driver

If this doesn’t work, you can also try to download the driver for your device from the manufacturer’s website.

Way 2. Check and fix hard disk internal error or file system error

To check and fix hard disk internal error or file system error, you can try the following two methods.


First of all, press Win+R at the same time to open Run, input “cmd” and hit Enter (be sure to run it as an administrator). Then type "chkdsk g: /f /r /x".

Chkdsk Check Error

g: refers to the drive letter of the drive that you need to check
/f fixes the errors found in the F partition/volume.
/r locates the bad sectors on the drive and recovers readable data. But some data cannot be recovered with /r. So it is important to develop a habit of making schedule backups.
/x forces the drive to dismount before the process starts.

B. Check and fix the hard drive error via AOMEI Partition Assistant

If you are not familiar with such computer administrating jobs, you can turn to a third-party tool. AOMEI Partition Assistant Standard is highly recommended. It can run on Windows 10/8/7/XP/Vista. With a neat and tidy interface, this software is quite easy to use for both computer experts and newbies. To check and fix the hard disk error via AOMEI Partition Assistant, do as follow:

Download Freeware Win 11/10/8.1/8/7/XP
Secure Download

1. Download the freeware. Install and launch it. Right-click the drive partition you need to check, and select Check Partition under Advanced.

Advanced Check Partition

2. Choose check partition and fix the error in this partition by using chkdsk.exe or the other two options based on your needs. Then click on OK, and wait until completed.

Check Partition and Fix Errors

Bonus tip: you can also right-click the disk which shows as unallocated space, and choose Surface Test to check whether there is bad sectors on the hard drive.


Way 3. Recover the unallocated space via partition recovery software

When your hard disk partition is deleted by accident, it will become an unallocated space, too. Thus you can upgrade the AOMEI Partition Assistant Standard version to Professional one, which can recover deleted partition within simple steps. Of course, the inside data will also be back as long as you don’t overwrite any data onto it after the unallocated space issue.

1. Install and launch AOMEI Partition Assistant Professional. Click on RecoverPartition Recovery.

Partition Recovery

2. Then select the disk that shows unallocated space and click Next.

Select Disk

3. In this window, choose a way to search the lost partition. Here we choose the first one. And click Next.


4. Now, tick the lost partition you want to recover and click on Proceed.

Select Lost Partition

5. When the lost partition has been recovered, click Finish.


Then, you can find the unallocated space will turn into a partition and the inside data can also be accessed.

Way 4. Repair unallocated disk space by creating a new partition

If none of the above hard disk unallocated repair methods work, you can directly create a partition on the unallocated space again. But that will erase all data on the disk, so it is necessary to recover the data from unallocated hard drive using a reliable recovery tool first. Then you can use the above partition manager to create a new partition.

1. Run AOMEI Partition Assistant, right-click the unallocated space on the hard drive and select Create Partition.

Create Partition on Unallocated Space

2. Set the drive letter, size and file system of the hard drive as you wish and click OK.

Edit New Partition

3. Back to the main interface, click Apply to commit the operation.

Or you can merge this unallocated space into another partition through the "Merge Partitions" function.

Merge Partitions

Way 5. Delete volume

Sometimes the volume may need to be manually deleted. AOMEI Partition Assistant Standard can also help you.

Step 1. Launch AOMEI Partition Assistant. In the main interface, right-click the partition, and choose “Delete Partition”.

Delete partition

Step 2.  In the pop-up window, choose “Delete partition quickly without wiping data” or “Delete partition and wipe data on it”. Then, click “OK”.

Quick Delete

Step 3. Click “Apply” and “Proceed” to confirm the operation.



With those available methods, the hard disk unallocated repair will be completed in Windows 11/10/8/7. So don’t feel overwhelmed next time when you encounter such errors. Besides repairing hard disk unallocated errors, AOMEI Partition Assistant easily deals with many other hard disk errors, like USB drive showing 0 bytes, non-system disk error, etc. Most importantly, its Server edition provides many more features you will need for effective disk/partition management on Windows Server 2003, 2008 (R2), 2012 (R2), 2016, 2019, and 2022.