How to: Recover External Hard Drive Unallocated Space in Windows

External hard drive show as unallocated space in Windows 7/8/10 Disk Management? How to recover the unused disk space? This tutorial will show you how to fix external hard drive unallocated space in different situations.


By Lucas / Updated on May 12, 2023

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External hard drive unallocated space appears in different situations

The external hard drive with 2 terabytes could count as the dividing line for those situations that will be discussed in this part. One is the external hard drive with a size less than 2 TB has unallocated space. It also might has partitions like G drive, H drive, and then has unallocated space on external hard drive. In this condition, you can either add the unallocated room to partition or create new partition with that space.

The other is external hard drive with the size more than 2 TB, say 3 TB drive, has unallocated space. This space could be treated as above drive if the partition table is GPT instead of MBR type because MBR disk supports the capability up to 2 TB while GPT style doesn’t have this limitation. If not, you need convert MBR disk to GPT disk to make use of the unallocated space.

The last situation that external hard drive has unallocated space would be new bought hard drive. Every drive should be formatted and partitioned before you use it. Therefore, you can try quick partition the new external hard drive.

How to use unallocated space on external hard drive?

For external hard drive whether overpass 2 TB or not with used partitions and unallocated space, the solutions aim to them have little difference after partition table converting. Therefore, two specific solutions will be illustrated in next part, one is for add unallocated space to partition, the other is for quick partition new drive.

Add unallocated space to partition on external hard drive

Check out the location of the unallocated room in the Disk Management. If the unallocated space is adjacent to the target partition from the right side, you can use Disk Management to finish this job directly. Right-click the designed partition, select Extend Volume. Then drag the arrow to cover the unallocated space, and then click OK. If the unallocated space is separated by other partitions on the disk, you need to turn to third party software now. AOMEI Partition Assistant Standard is free partition manger for Windows XP/Vista/7/8/10. It can solve this issue with Merge Partitions feature. Download it to have a try.

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Step1. Install and launch Partition Assistant. Right-click the unallocated space, and select Advanced > Merge Partitions.

Merge Partitions

Step2. Check the unallocated space as well as the target partition. You can select any partition of them as the target partition.

Select Target Partition

Step3. Now you got 255 GB in D drive. Click Apply to execute the pending operation.


Quick partition new external hard drive

In order to reach this goal, you also got two ways, Disk Management and AOMEI Partition Assistant Standard. In Disk Management, right click the new drive, and select New Simple Volume. Then pop-up window of creating new simple volume will come into your sight. The rest you need to do is follow the wizard, in which you will decide the partition size, assign the drive letter and choose the file system. This process will format this external hard automatically. If you want to create more than two partitions in this hard drive, then you need to repeat above steps. Or, you can try another easy and fast path. Do quick partition using AOMEI Partition Assistant Pro.

Step1. Install AOMEI Partition Assistant Pro. Right click the new drive and select Quick Partition.

Step2. Configure specific partition settings (partition numbers, disk type, partition size, and partition labels) in this window. Click Start Partitioning after your configuration.

Specify Quick Partition

Step3. Wait the process to be finished for a few minutes, and then you will see the outcome.



No matter in what situation you have an external hard drive unallocated space, AOMEI Partition Assistant could help you make use of it. With this freeware, you can reformat to FAT32 from NTFS file system. You even can do above operations on the internal hard disk in which the OS is on. This software has many helpful features, such as migrate OS to SSD, copy disk/partition, Windows To Go creator and so on. By the way, this freeware supports only Windows PC operating systems. If you’re running Windows Server like Server 2003/2008/2011/2012/2016/2019, you might as well turn to AOMEI Partition Assistant Server which specially designed for Server users.

Lucas · Staff Editor
I prefer peaceful and quiet life during vacation,but sometimes I watch football match if my favorite club performs brilliantly in that season. And I love reading, painting and calligraphy, thus I send my friends festival handwriting cards every year.