Why am I unable to convert my drive to GPT?

Question

I have a 4TB (2TB unable to be allocated) data disk drive (disk 3) formatted with MBR and need to convert it to GPT so that I may expand the volume to the full 4TB. I have opened diskmgmt.msc as Administrator per the instructions given here: https://learn.microsoft.com/en-us/troubleshoot/windows-server/backup-and-storage/support-for-hard-disks-exceeding-2-tb#convert-an-mbr-disk-to-gpt
However the "Convert to GPT" option is still greyed out when I right click Disk 3 on the bottom. What am I missing?

Answer 1

As per https://learn.microsoft.com/en-us/windows-server/storage/disk-management/change-an-mbr-disk-into-a-gpt-disk

You can change a disk from MBR to GPT partition format as long as the disk contains no partitions or volumes.

You need to delete the existing partition first.

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hth

Marcin

Answer 2

Hi Matt Brossette,

Thanks for your post. The option to convert a disk to GPT (GUID Partition Table) may be grayed out in Windows Disk Management if the disk is currently in use, has partitions that are not supported by GPT, or if the disk is smaller than 2TB. To resolve this issue, you can try to make sure that all partitions on the disk are deleted, remove any volumes or drive letters assigned to the disk, or disconnect the disk from the system temporarily. You can also use third-party partition management software to convert the disk to GPT. If you do still want to set that drive up with a GPT partition style, try this process, please note this will delete any data on that drive.

Click your Start Button, then just type cmd. On the resulting list, right click Command Prompt and select 'Run as Administrator'.

1. Run this command and hit Enter: diskpart
2. Run this command and hit Enter: list disk (Make note of the disk number you want to convert and enter it into the next command - replace X)

3.Run this command and hit Enter: select disk X

4. Run this command and hit Enter: clean
5. Run this command and hit Enter: convert gpt

Then close Command Prompt

Best Regards,

Ian Xue

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