MBR2GPT failing on your storage drive is not a bug and not a broken disk. The tool only speaks to the disk Windows boots from. Data disks take different roads — pick yours with your eyes open about which ones erase.
The giveaway is in Microsoft's own requirement list: validation demands that the BCD store on the system partition contains a default OS entry. Your D: drive full of photos has no BCD and no OS entry, so it fails that check instantly and forever. MBR2GPT converts the Windows system disk — only that disk. If a data disk needs GPT — typically because it is larger than 2 TB, the classic MBR ceiling — here are the routes, labelled honestly by what they do to the data.
👆 The failure is the tool correctly recognising a disk it was never built to touch
The built-in Windows tools only convert a disk that has no partitions on it. That makes the free, official route a logistics exercise:
select disk 1 then clean — with the disk number triple-checked, because clean is instant and total.convert gpt).Slow, boring, and completely safe when the copy is real. For a disk you were going to reorganise anyway, this is often the right answer.
Various partition tools advertise one-click MBR-to-GPT conversion of data disks without deleting partitions. Many of them work, most of the time, on most disks. The honest conditions:
If the disk holds the only copy of anything, Route 2 is the wrong route at any price.
People hesitate here unnecessarily: Windows reads and writes GPT data disks perfectly well even when the PC itself boots in Legacy mode. UEFI is a requirement for booting from GPT, not for using a GPT disk as storage. So a 4 TB drive converted to GPT for its full capacity will work in the same machine, on the same day, with no firmware changes and no effect on your Windows disk. The conversion question for a data disk is only about the data's safety during the switch — never about boot modes.
Under 2 TB, with four or fewer partitions and no complaint from any software, an MBR data disk is not a problem waiting to happen — it is a finished decision from an earlier era that still works. The honest triggers for converting a data disk are: capacity above 2 TB being wasted, a need for more than four primary partitions, or standardising a technician's whole bench on one style. "It feels old" is not on the list.
The video covers the system-disk half of this world; pair it with this page and both of your disks have an honest route to GPT.
▶️ Watch Full VideoBy design. One of its documented requirements is a BCD store with a default OS entry on the system partition — something only the Windows system disk has. The tool converts that one disk; data disks use the routes on this page.
Yes. UEFI is required to boot Windows from a GPT disk, not to use one for storage. Windows on an MBR system disk can read and write a GPT data disk normally — which is exactly how large storage drives are used in older machines.
No. That option only works on a disk with no partitions, so the data must be copied off first and restored after. Any tool that converts a data disk with the files in place is a third-party tool, with the cautions described above.