How to Fix the Disk Signature Collision Error on Windows

A disk signature is also known as an HDD signature, Disk Identifier, Unique Identifier (UID) and fault tolerance signature. It is a unique identifier stored as part of the MBR (Master Boot Record). They are used by the operating system to identify and distinguish between storage devices. It is commonly made up of eight alphanumeric characters.

What Is a Disk Collision?

A disk collision occurs when your operating system (Windows) detects that there are two disks with identical signatures. Windows may not always prompt the user when a collision occurs. In previous versions of Windows (like Windows Vista and XP), when a collision occurred the signature of the drive complaining of a collision would be changed automatically. Windows cannot permit two disks with the same signature to coexist and function at the same time. For Windows 7, 8, 8.1 and 10, it disables the second drive and does not allow it to mount until the disk collision has been rectified.

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If you have a disk collision issue, you might see one of these two messages: “The boot selection failed because a required device is inaccessible” or “This disk is offline because it has a signature collision.

These messages are usually seen from the Disk Management tool when a collision occurs. If your default boot drive goes offline as a result of a collision, then the computer becomes unable to boot properly. A 0xc000000e error is displayed at startup.

What Causes Disk Collision?

Although Disk collisions are a rarity, they can happen to you if you run a disk that has been cloned alongside its clone. Something similar can happen if you make a virtual hard drive from a physical one or use back up software that uses virtualisation.

How to Fix the Disk Signature Collision Error in Windows

1. Open Command Prompt or Windows PowerShell as an Administrator.

2. Type Diskpart in the command prompt window, and hit the Enter key.

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3. Type list diskand press Enter. This will list all the disks that are currently on the system.

This is a list of actual physical disks and not partitions. It’s the same list you’d see under the Disk Management window.

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4. Type select disk x (where “x” is the number of the problem disk) and hit Enter. If you’ve done this successfully, Diskpart will display this message: “Disk x is now the selected disk.”

For clarification, if you typed in select disk 0, it will display “Disk 0 is now the selected disk.”

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5. Type Uniqueid disk and hit Enter. This will display the disk’s signature.

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6. Type unique disk ID={NEW SIGNATURE},  where “{NEW SIGNATURE}” is the new ID you want for the disk (without the curly brackets).

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The Disk Signature must be in the form of a hexadecimal figure.

If it isn’t in the right format, DISKPART will throw an error that reads: “The specified identifier is not in the correct format. Type the identifier in the correct format: in hexadecimal form for an MBR disk or as a GUID for a GPT disk.”

Once you’ve followed these steps correctly, Windows will put the disk online and assign a drive letter to it. A reboot may be required.

Final Word

Although Disk collisions are a rarity, it can happen if you are not aware and leave you with a computer that cannot be booted. If you are having a disk collision issue in Windows, the method above seems to be the most surefire and low-risk way to sort this issue out.

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2 comments

  1. Thank you very much! This is exactly the problem I was facing after cloning two HDDs that I wanted to mount simultaneously.

  2. Wonderful! This is the clearest and most straight-forward solution to a surprise problem. Followed the instructions (except used the Offline disk # of course), rebooted, and Voila! Thanks so much.

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