How to Repair and Restore Unallocated Space on a USB/SD Card

Tracy King updated on Sep 10, 2020 to Partition Manager | How-to Articles

Applies To: USB, SD Card, Pen Drive, and Other Removable Storage Devices

Problem: USB/SD Card Stops Working, Showing As Unallocated

Have you ever met this problem that your SD card or USB drive suddenly shows as unallocated or even stops working on your PC? Afterward, you can neither access data nor save new data on it. Many users have encountered the issue that a used storage device, like a hard disk, USB, SD card, or pen drive, is missing under File Explorer and is marked as "Unallocated" in Disk Management, which is quite confusing and annoying.

What Is Unallocated Space on a USB/SD Card

"Unallocated" is a state indicating that this part of space on the storage device hasn't been formatted and partitioned yet and thus is not ready for data storage. You can neither access the unallocated space under the computer drives or write data to it. To utilize unallocated space, you can either create a new partition using the space or add it to an existing partition.

When Will You See Unallocated Space

As mentioned, the space that is not assigned to a partition by Windows is called "unallocated space". Therefore, the space on a newly initialized disk or the space that is left free will all show as "Unallocated". An existing partition on a hard drive, external hard drive, USB, SD card or other removable disks may also become unallocated space after some operations.

Why Does a USB/SD Card Become Unallocated Suddenly

The commonest reasons are deletion and virus attack. For example, you may accidentally delete the partition on the USB or some program does this for you. It's also possible that you were doing some operations that required you to delete partitions but you didn't realize it. Besides, it's not surprising that malicious virus attacks may bring various negative results, including a USB becoming unallocated.

In such cases, data loss always coincides with the partition's change to unallocated space. Fortunately, you can repair an unallocated USB or SD card and retrieve your files with ease.

How to Fix and Repair an Unallocated USB/SD Card

Depending on whether you need to perform data recovery, there will be different solutions for you.

Method 1. Create a New Partition Directly

If the USB is brand new or you have no intention to perform data recovery, you can create a new partition using the allocated space directly to make the space usable.

To create a partition using unallocated space on a USB/SD card:

Step 1. Connect or insert the USB/SD card to the computer.

Step 2. Go to "This PC", right-click it and choose "Manage" > "Disk Management".

Step 3. Right-click the unallocated space and choose "New Simple Volume".

Step 4. Follow the wizard to finish the remaining process.

Create a new partition on unallocated space

You can also partition an unallocated USB/SD card using third-party software. 

Method 2. Restore the Partition from the Unallocated USB

However, if you attempt to repair a used USB or SD card that contains precious files and becomes unallocated unexpectedly, you should perform data recovery.

To recover both the files and the partition on the USB all at once, perform a partition recovery using the partition tool - EaseUS Partition Master is a workable choice for you. EaseUS Partition Master will restore both the data and the partition for you from the unallocated space on the USB or SD card. Thus, it spares you the steps to create a volume manually. (Or you may want to recover data from the unallocated space only and then create a volume as you like.)

To repair the unallocated space on the USB/SD card:

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 Windows 10 is supported


Step 1: Connect the external storage device to PC

Connect the USB, SD card or external hard drive on which you lost partition to your computer.

Step 2: Launch EaseUS Partition Master

On the main interface, click on "Partition Recovery".

Run EaseUS Partition Master for partition recovery

Step 3: Select the storage device to scan the lost partition

Select the SD card, USB or external hard drive on which you deleted or lost partition and click "Scan".
And wait till the scanning process completes.

Scan lost partitions

Step 4: Select and restore lost partition.

1. Double-click the found partition, marked as Deleted with the previous Label, to check its content, and then click "Proceed" to continue.

Check lost partition data

2. Click "Recover Now" to restore the lost partition and data on your SD card, USB or external hard drive.

Scan lost partitions

3. Click the "Execute Operation" button and click "Apply" to restore lost partition on the target storage device.

Scan lost partitions

Knowledge Base: Unallocated Space VS Free Space

Both the unallocated space and free space you see in Disk Management are unusable spaces. When you shrink a logical partition, you will get free space, while a primary partition the unallocated space. Based on the information, you can easily conclude that they are identical and both unallocated space and free space are actually "unallocated" space. 

In addition, free space may also refer to the unused space in an existing partition, disk, or external storage device. It's usable compared with the chunk marked as free space in Disk Management.

The Bottom Line

Conclusively, you can fix an unallocated USB/SD card/pen drive by establishing a new volume. One thing you need to consider is whether you need to recover data from the unallocated space. If you do, use software like EaseUS Partition Master to restore your partition (including data) or use EaseUS Data Recovery Wizard to recover only data from the unallocated removable disk.

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Frequently Asked Questions

Why Choose EaseUS Partition Master?

"I've used Partition Master Professional many times to create, delete, format, move, rename, and resize partitions."PCWorld

"Partitioning tools have come a very long since the days of complicated command line utilities and EASEUS Partition Master is one of the most advanced programs available."TECH ADVISOR

"I love that the changes you make with EaseUS Partition Master Free aren't immediately applied to the disks. It makes it way easier to play out what will happen after you've made all the changes."Lifewire

Will the "Migrate OS" feature transfer the Windows system files only or the whole C drive?

To ensure that the migrated system will boot normally, the Migrate OS feature will transfer all the files in the system and the boot partitions. Generally, the boot partition is the C drive so the transfer will include all the files in C.

Does EaseUS Partition Master license apply to multiple computers?

The license of Partition Master Professional and Server editions can be used on 1 computer only, while that for for the Technician and Unlimited editions can be used on multiple machines.

What is the difference between EaseUS Partition Master Trial version and the Free version?

Free is for home users only, with most basic functions available such as partition resize and clone. While trial can help you understand how this product works and test what a full license can do on a business or server OS machine.

Will it cause any data loss after resizing the partition in EaseUS Partition Master?

Generally, it will not cause any data loss or boot issue by resizing a partition. However, in order to protect your data, we suggest that you backup the partition before resizing, in case of any unexpected situations such as power outages, computer hardware failures, etc. You can use EaseUS Todo Backup to backup the partition and its trial version is fully functioned for 30 days.

What should I prepare before resizing the partition?

On the partition that is going to be operated, there might be some files being occupied by other programs. To ensure a successful operation, we suggest that you close all the unnecessary software before resizing that partition. Otherwise, EaseUS Partition Master will detect the partition being locked by the other software and require a reboot to resize the partition under boot mode.

About EaseUS Partition Master

All-round disk & partition management software for personal and commercial use. Let it manage your storage drive: resize, format, delete, clone, convert, etc.

Video Tutorial

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