Fixing 'The selected disk is not a fixed MBR disk' error in diskpart

The error "The selected disk is not a fixed MBR disk" primarily occurs when Windows identifies the disk as "removable" instead of "fixed," regardless of partition style. 2. To fix it, ensure the disk is connected internally via SATA or NVMe, not through a USB adapter, and appears as "Fixed" in DiskPart's list disk output. 3. Check for proper SATA port usage, update motherboard firmware or drivers, and disable USB 3.0 emulation in BIOS if needed. 4. Use Windows Storage Spaces or third-party tools like Macrium Reflect if DiskPart operations fail due to the removable flag. 5. Avoid the registry workaround unless experienced, as editing the disk enumeration can risk system instability. 6. Convert the disk to dynamic only after confirming it's recognized as fixed, since mirroring requires both dynamic and fixed status. The root issue is disk classification, not MBR/GPT—native mirroring in DiskPart will fail on removable-labeled disks, so changing hardware or using alternative software is often necessary.

The "The selected disk is not a fixed MBR disk" error in DiskPart usually appears when trying to perform certain operations—like creating a mirror or extending a volume—on a disk that doesn’t meet specific requirements. This error can be confusing, especially if you're working with what you believe is a standard internal hard drive. Here's how to understand and fix it.

What the Error Really Means

Despite what it sounds like, this error isn’t just about MBR vs GPT or partition style. The key part of the message is "not a fixed MBR disk"—but “fixed” here doesn’t refer to the file system or partition table. In Windows disk terminology, "fixed" means a physically attached internal hard drive, as opposed to removable or external drives.

So, even if your disk uses MBR, if Windows detects it as "removable" (like a USB drive), DiskPart will block certain operations (especially RAID/mirror-related commands like add mirror) and show this misleading error.

Common Causes

• The disk is externally connected (e.g., via USB-to-SATA adapter).
• The motherboard or driver identifies the internal disk as removable.
• The disk’s hardware flag (Removable Media Bit) is set incorrectly.
• Using virtual machines or certain SATA/USB enclosures that emulate removable storage.

How to Fix It

1. Check Disk Connection and Type

Ensure the disk is:

• Connected directly via SATA or NVMe (not USB).
• Installed internally, not through a USB adapter.
• Recognized as an internal drive in Device Manager.

If you're using a USB-to-SATA cable, switch to a direct SATA connection if possible. Many USB enclosures cause Windows to label the disk as "removable," triggering this error.

2. Verify Disk Attributes in DiskPart

Open Command Prompt as Administrator and run:

diskpart
list disk

Look at the output. If your target disk shows "Removable" under the Type column, that’s the issue.

Example:

  Disk 1    Removable  1000 GB     0 B

Even if it's a full-size internal drive, this label will block mirror operations.

3. Check for Hardware-Level Fixes

Some motherboards or chipsets misidentify SATA drives as removable. Try:

• Plugging the drive into a different SATA port (preferably non-USB-based).
• Updating motherboard firmware or SATA drivers.
• Disabling USB 3.0 emulation in BIOS if applicable.

4. Use a Different Tool (If DiskPart Won’t Work)

If you're trying to create a mirror (RAID 1), and DiskPart fails, consider using:

• Windows Storage Spaces (Settings > System > Storage > Advanced storage settings > Disks & volumes > Storage Spaces)
• Third-party tools like Macrium Reflect, AOMEI Backupper, or EaseUS RAID tools

These tools are often more flexible with disk types and can create mirrors even when DiskPart refuses.

5. Registry Workaround (Advanced – Use Caution)

In some cases, you can override the removable flag using the registry, but this is risky and not guaranteed.

1. Open Registry Editor (regedit) as admin.
2. Navigate to:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\disk\Enum

3. Look for entries referencing your disk and check if it's labeled as removable.
4. Warning: Editing this incorrectly can break system stability. Only proceed with backups and expertise.

Alternatively, some users have success using third-party tools like HWiNFO or USB Drive Letter Access to force-clear the removable bit, but results vary.

Alternative: Convert to Dynamic Disk (For Mirroring)

If you're trying to create a mirror, the disk must be dynamic, not basic. But you can’t mirror on a "removable" disk even if it's dynamic.

Steps:

1. In DiskPart:

   select disk X
   convert dynamic

2. Then try:

   select disk X
   add mirror disk=Y

   But again, if the disk is flagged as removable, this will still fail.

   ---

   Bottom Line

   The error is misleading—it's not really about MBR. It's about disk type classification. Windows blocks certain operations on disks labeled as "removable," regardless of their actual use.

   Best solution:
   Ensure the disk is connected internally via SATA or NVMe, appears as "Fixed" in diskpart list disk, and is set to AHCI mode in BIOS. If it still shows as removable, the hardware or enclosure may be the root issue.

   Basically, if DiskPart sees it as removable, you’re out of luck with native mirroring—switch tools or hardware.

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