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

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.

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:

Step 1. Connect the external storage device to your computer for lost partition recovery. To begin with, click "Partition Recovery" on the top menu. Then choose the target disk and click "Scan".

Step 2. EaseUS Partition Master will scan and display all the partitions that are existing and lost under the selected disk. You can choose the partition that clearly shows as "Lost" in the "Status" tab and click "Proceed".

Double-click on a partition will allow you to preview the content.

Step 3. Click "Recover Now" as along as all the lost data has been found. If not, go on with the "Continue Scanning" option.

Step 4. Wait the software processing the final recovery. After that, click "Finish".

Step 5. Your lost partition should reappear in the drive.

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.