By Dylan / Last Updated March 25, 2020

Disk is unknown and not initialized

In some cases, when you view your hard disk in Disk Management, you might only find that the disk is unknown and not initialized, just as the following two screenshots show:

1. Unknown, Not Initialized and no disk space.

2. Unknown and Not initialized and the space is unallocated.

Why disk became unknown and not initialized?

Generally, the issue that your disk became unknown and not initialized can be caused by the following reasons:

● Virus and malware

● Corrupt MBR

● Sectors damaged

● Partition loss

No matter what reason causes this issue when your disk became unknown and not initialized, you will receive the error “You must initialize a disk before Logical Disk Manager can access it". Therefore, you are not allowed to access your disk before initializing it to MBR or GPT. But initialization will erase all data you have stored on the disk. Luckily, this article will show you how to initialize disk to MBR or GPT without losing data.

What happens when you initialize a hard disk?

Initializing a hard disk is a process of rebuilding its MBR (Master Boot Record), where the file system, logical partition, and other basic information are kept. And the data on the hard disk will be deleted on the front sectors of the disk changed. Besides, the disk cannot store any data until it gets partitioned.

If there are some important data that you don't want to lose, you might need to retrieve the data from it and keep them in another safe place to avoid data loss. Then you can initialize the disk to MBR or GPT.

How to initialize disk MBR or GPT without losing data?

Before initializing disk which contains important data, in the first step, you might need to retrieve the data from it and transfer them to another safe place. Then you can initialize disk MBR or GPT without data loss.

Step 1. Retrieve data from the “Unknown and Not initialized” disk

To recover data from a damaged disk, you can try rel="nofollow"">RecoveritPro, which is a reliable data recovery tool with 96% recovery rate. With a few steps, you can easily recover any type of data from an uninitialized disk.

Install and open the Recoverit Pro, and choose “External Device Recovery” to recover the data on the disk. When it is finished, you can initialize disk MBR or GPT without losing data.

Step 2. Initialize disk MBR or GPT in Windows 10/8/7

After getting back vital data from the to-be-initialized disk, now you can refer to the following 2 methods to initialize disk MBR or GPT without losing data. Here are the specific steps.

Note: If your disk is smaller than 2TB and your computer boots with BIOS, you should choose MBR on the prompt, otherwise, choose GPT. You can go to this page to know more about MBR and GPT: MBR vs GPT: Which One is Better for You.

Method 1. Initialize disk MBR or GPT via Disk Management

The common method to initialize disk is using Disk Management. Now follow the steps:

1. Right-click the “This PC” icon, and choose “Manage”. In the Manage window, click “Disk Management” under the storage.

2. Right-click the unknown and Not Initialized disk, and select “Initialize Disk”.

3. In this Window, choose MBR or GPT as your partition style, and click “OK”.

Method 2. Initialize disk MBR or GPT with AOMEI Partition Assistant

In addition to initializing disk via Disk Management, there is a disk manage tool-AOMEI Partition Assistant Standard. Its intuitive interface and full features allow you to successfully initialize disk MBR or GPT with a few simple steps. Let me guide you on how to do it.

1. Open AOMEI Partition Assistant and right-click on the uninitialized disk. Then select “Initialize Disk”.

Disk Initialize

2. In the pop-up windows, you can choose MBR or GPT to initialize. You choose it according to the disk.

Choose Disk Style

3. Click “Apply” on the top left of the Window, and wait for the process to complete.

Apply Initialize

Step 3. Create a partition on the disk

After initializing this disk, you can also use the AOMEI Partition Assitant to create a partition.

  1. Launch AOMEI Partition Assistant, right-click on the disk you just initialized and choose "Create Partition" on the drop-down menu.

Create Partition

2. You can adjust the size of the new partition. When you finish it, click "OK".


3. Then click "Apply" > "Proceed" in the main interface.


Other methods to fix unknown and not initialized disk

Since the unknown and not initialized problem may be caused by several reasons. In some situations, you don’t need to initialize disk to fix it. Instead, you can try some other methods to tackle this problem.

Method 1. Scan disk for virus and malware

Sometimes, a disk became unknown and uninitialized because it is infected by virus or malware. You can check your computer with anti-virus software.

Method 2. Rebuild MBR

If the MBR (master boot record) of your disk is corrupted, you will see the disk is unknown and not initialized, and system cannot access the disk. Then you can also utilize the AOMEI Partition Assistant to rebuild MBR to fix the error.

Step 1. Open AOMEI Partition Assistant, and right-click the unknown and not initialized disk, then select “Rebuild MBR”.

Rebuild Data Disk Mbr

Step 2. Select the current operation system, and click “OK”.

Step 3. Click “Apply” and "Procced" to start rebuild MBR.


Method 3. Fix bad sector

If there is a bad sector on your disk, computer can’t write and retrieve data on the disk, and the disk shows no space. With AOMEI Partition Assistant, you can check the disk whether there is a bad sector on it. Then repair the bad sector with CHKDSK command in CMD. Here are the steps:

Step 1. Open AOMEI Partition Assistant, and right-click the disk you want to check, then select “Surface Test”.

Surface Test

Step 2. Then, you can choose “Quick Check” which is much faster, and click “OK” to start.

Start Test System Disk

Step 3. Press "Windows + R" and input "CMD" to open Command Prompt

Step 4 . And execute the following commands to fix bad sector:

  • sfc /scannow

  • chkdsk c: /f /r

  • bootrec /fixmbr

  • bootrec /fixboot

  • bootrec /scanos

  • bootrec /rebuildbcd

Method 4. Recover deleted/lost partition

Partition loss is one of the other factors that can make disk unknown and uninitialized. If it is the real cause in your situation, you can upgrade to AOMEI Partition Assistant Professional, which can help recover deleted partition.

Partition Recovery Wizard


This is how to initialize disk MBR or GPT without losing data in Windows 10/8/7. If you encounter the issue that disk is unknown and uninitialized, you should firstly recover the data on the disk, then initialize the disk.

Meanwhile, as you can see, AOMEI Partition Assistant is an all-in-one tool that provides lots of features to manage disk. If you upgrade to professional edition, you can unlock more functions: convert system disk to GPT without losing data, wipe system disk, migrate OS from MBR disk to GPT, etc.