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How to partition a Windows drive that was previously formatted in Mac?

How to partition a Windows drive that was previously formatted in Mac?

Mac OSX may create an extra 200 MB EFI partitions at the start of a drive hence you may see this EFI partition in Windows. The Windows Disk Management tool can’t delete these EFI partitions, and you’ll see the “Delete Volume” option grayed out. This article describes how you can clean these partitions in DOS command mode and re-format your CalDigit drive.

IMPORTANT NOTE: Following the procedure below will ERASE ALL DATA on the drive. Prior to following these directions, verify important data is stored securely on a different storage device.

In Windows, you can remove an EFI System Partition or GPT Protective Partition from a Drive that was previously formatted and used in Mac OSX by following the procedures below:

1. Connect your CalDigit drive to your Windows computer.

2. Open Disk Management: Control Panel -> Administrative Tools -> Computer Management -> Disk Management.

An image of 2 drives in the Disk Management tool with 200MB reserved for EFI on one disk.

3. Find the CalDigit drive that you want to format in the list of drives. To verify the drive, you can right click on Disk number -> Properties. In the popup window, you will see the device information. Take CalDigit Tuff drive as an example, you should see “CalDigit Tuff Device”.

4. Launch DOS Command mode from Windows.

An image of Command Prompt in Windows search.

5. Type a command called “diskpart” and hit enter. This launches the diskpart command-line utility used for advanced disk partitioning tasks. You’ll see the prompt change to “DISKPART” afterward.

"diskpart" typed in to the Command Prompt, per step 5.

6. In DiskPart prompt, type list disk, then press enter. Doing so will display a list of all hard drives attached to the system, the size of the disks, and the disk number assigned. Note the disk number of the CalDigit drive with the 200MB EFI partition. If you used the Disk Management to find this number earlier in step 3, it should be the same number.

A visual representation of DiskPart steps 6, 7, and 8.

7. Select the drive you want to partition. In this example, we type in “Select Disk 1” and hit enter. Be very careful that you select the correct disk number. You wouldn’t want to accidentally wipe the wrong disk.

8. Type in a command called “clean” and hit enter. This “cleans” all partition information from the selected drive, effectively wiping it and turning it into one big, unpartitioned chunk of space.

9. Type “exit” to quit the DiskPart command mode.

10. Now back to Windows Disk Management, you will see the drive becomes a big chunk of “Unallocated” space.

Disk Management Tool with the EFI portioned drive now completely unallocated.

11. Right-click the Disk Number and select “Initialize Disk.”

The previous drive has been right clicked and says "Initialize Disk"

12. Choose either the GPT or MBR partition style for the disk.

The Initialize Disk menu, showing partition styles MBR (Master Boot Record) and GPT (GUID Partition Table)
A close-up of the Unallocated drive in Disk Management

13. After drive initialization, right click on “Unallocated” area and choose “New Simple Volume…” to format the new volume. Follow the pop-up Wizard to finish the drive format.

The unallocated drive in Disk Management after being right clicked and showing "New Simple Volume..."

14. The new drive volume with full drive capacity will mount on your Windows system.

The now allocated drive ready to utilize.

Additional Information: DiskPart command

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