By Emily / Last Updated February 19, 2019

Help! My external HDD suddenly became “unallocated”

Help me! I have my iomega 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.

Is there any way to fix my external HDD without losing files? I want to use my HDD again and also don’t wanna lose those files.please help me, thanks a lot.

--Extracted from sevenforums

Analysis about hard disk showing unallocated

Are you facing the same issue? When trying to use the drives, it shows as unallocated suddenly for no reason. What does this means? This means the data is there, but you cannot access it. Before attempting to fix it, we need to figure out what makes hard disk unallocated first.

There are many reasons that can cause hard drive showing as unallocated, and in many cases not even an expert can figure out why it happened. But the most common reasons are:

  • Infection with a virus or spyware

  • Removing the hard disk improperly

  • Hard driver is outdated

  • Hard drive internal error

  • File system error

Detailed guide for hard disk unallocated repair in Windows 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 windows 10/8/7 correspondingly.

1. Download and run the anti-virus software to clean up viruses in PC and external hard drive.

2. Removing or unplugging the external hard disk properly and carefully every time.

3. 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.

Device Manager

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

4. Check and fix hard disk internal error or file system error

If you tried every method listed above, but the hard disk still shows as an unallocated space, you need to check and fix hard disk internal error or file system error. Two methods are available for that.


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

Check Disk Error


f: refers 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 recover readable data. But some data cannot be recovered with /r. So it is important to develop 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 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:

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

Check Partition and Fix Errors

Bonus tips: 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.


If no error is found, you can repair the hard disk showing unallocated space by creating a partition. 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 software if you want to fix unallocated hard drive without losing data

To create partition, take the following steps.

(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.

Finally, the hard disk unallocated repair will be completed in Windows 10/8/7. So don’t feel overwhelming next time when you encounter such errors. Besides repairing hard disk unallocated error, AOMEI Partition Assistant easily deal with many other hard disk errors, like USB drive showing 0 bytes, non-system disk error, etc. Such a versatile is a “must” for anyone who always wants to manage their disk or partition with ease. 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 and more.