Windows 10: Converting from an MBT to a GPT partition table in preparation for a Windows 10 installation.

Hey everyone! Hope you all can help me out with this.

Excuse me if this is a rather elementary issue; I'm not particularly experienced with these sorts of issues.

I've been trying to install Windows 10 on my machine (currently running Windows 7) using a bootable USB, but I've run into a number of issues. Upon selecting my installation location I was greeted with the following error;

'Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks'.

From what I understand, my OS drive (on which I plan to dual boot Windows 7 and Windows 10) is formatted in the MBR partition scheme and I must convert the drive to a GPT partition table if I am to install Windows 10. I've determined that my system is UEFI-compatible, however, I am unable to switch between the UEFI and Legacy Boot modes in my BIOS settings.

I understand it is possible to make a backup of the drive, wipe the drive clean, and re-format the partition table that way, but seen as my ultimate goal is to dual boot the two operating systems I'd much prefer a solution that does not involve having to re-format the drive.

After much research, I found a command-line utility on GitHub called gptgen. This seems like it would suit my issue quite well, however, the read-me advises against using the utility on the OS drive due to boot issues between GPT and MBR. It instructs me to 'create a BIOS boot partition and install a GPT-aware boot loader' which I'm not quite sure how to go about doing. Does anyone have any ideas? Are there any other tools out there that might suit my purpose?

Thanks so much in advance.

TL;DR - ran into issues installing Windows 10 on an MBR drive, must convert to GPT. would prefer a solution that does not involve wiping the drive clean.

submitted by /u/ElementalFrosty
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:)

 

clone MBR HD to bootable GPT partition?

Hi,

1. You cannot convert mbr to gpt without data loss. otherwise, you can follow directions here:

FROM WINDOWS RECOVERY CONSOLE:

To change a master boot record disk into a GUID partition table disk using a command line

• 
  Back up or move the data on the basic master boot record (MBR) disk you want to convert into a GUID partition table (GPT) disk.
  
• 
  Open an elevated command prompt (right-click Command Prompt, and then click Run as Administrator) and type diskpart. If the disk does not contain any partitions or volumes, skip to step 6.
  
• 
  At the DISKPART prompt, type list disk. Make note of the disk number you want to convert.
  
• 
  At the DISKPART prompt, type select disk <disknumber>.
  
• 
  At the DISKPART prompt, type clean.
  

2. I'd suggest converting your vista drive to a virtual machine, load that up on your windows 10 system and use a program like virtualbox to run it.

 

Installing Windows Vista/7 on a GUID Partition Table

Background

GUID Partition Table (GPT) is a boot sector technology poised to replace the venerable Master Boot Record (MBR) principally because MBR has a maximum capacity of 2 TB for a single partition (some single disks have reached 3 TB). Installing Windows on a GPT is a bit tricky because Windows wants to default back to MBR. In order to force Windows on to a GPT, we have to pre-format the drive prior to Windows installation. You can do that during Windows setup using the console.

Requirements

• Windows Vista or 7 (must be 64-bit no matter which OS is used)
• A motherboard with EFI BIOS
• A means to EFI boot the Windows setup (I had to use a USB DVD drive on MSI Z77A-G65, the internal SATA Bluray drives didn't have an EFI option)

Instructions

• Boot into Windows setup using EFI. On the MSI Z77A-G65, it showed up as UEFI:USB-ATAPI DVD ... This will change according to your motherboard and how you are attempting to enter setup. This step is critical. Without booting into setup via EFI, only MBR is available to the setup. There's no easy way to tell from within setup if it is running via EFI or not.
• Once you have booted into setup, continue through the process as you would normally until you reach the dialog which shows you the available drives. Load a driver, if necessary, then press SHIFT+F10 to open the command prompt.
• In the command prompt, enter the following lines, pressing enter after each one. Note that the <id> field below is the disk ID that you want to format as GPT from the "list disk" command. If there's only one drive, <id> will likely be 1. Note: All data on the drive will be lost during this process. Make sure to select the correct drive.
  • diskpart
  • list disk
  • select disk <id>
  • online disk
  • attributes disk clear readonly
  • clean
  • convert gpt
  • create partition efi size=102
  • create partition msr size=32
  • create partition primary
  • format fs=ntfs label="Operating System"
  • assign letter=C
  • exit
  "online disk" and "attributes disk clear readonly" are likely to fail. Don't worry, they are only precautionary. Change the drive letter and label to whatever you want. Also, the above command (specifically "create partition primary") will consume all remaining space on the drive. If you want multiple partitions with fixed sizes, substitute what you want in place of "create partition primary."
• You may now close the command prompt and click on "Refresh" back in the dialog to choose where to install Windows. You should now see at least 2 partitions (I think Microsoft Reserved is hidden) and it will only let you install on a non EFI/MSR partition. Click on the primary partition and proceed with the installation as normal.
• Note that in the EFI BIOS after installing Windows via EFI, you can no longer directly boot the volume Windows is installed on. Instead, you must boot via "Windows Boot Manager" (on MSI Z77A-G65, it was "UEFI: Windows Boot Manager"). Keep that in mind if you wish to tweak the boot order.

Conclusion

That should do it. You should be in Windows with >2 TB of hard drive capacity available if you had more than 2 TB on the Windows partition. Congratulations being on the bleeding edge of technology! *Rockout :rockout:

 

Cannot convert GPT to MBR.

Hi Michael,



I suggest you to follow the below steps and check if it helps.

This method you have to backup all your data and delete all partitions and volumes. Then use the
DISKPART command.

• Open command prompt and type in DISKPART and press Enter
• Then type in list disk (Note down the number of disk you want to convert to GPT)
• Then type in select disk number of disk
• Finally type in convert gpt.

Hope the information helps. Do reply if you need further assistance.