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Converting from MBR to GPT (OS already installed)

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Is it possible to convert a SSD disk that already has Windows 10 on its first partition from MBR to GPT so that the OS is still bootable?

I want to place another iteration of Windows 10 on an empty partition of that disk by installing Win7 onto the empty partition and then letting it free upgrade to Win10. But the Windows 7 OEM System Builder Pack that I bought when I built my computer won't allow the installation because I am using UEFI boot mode and my SSD is MBR. Microsoft’s error message says the disk I want to install to needs to be GPT because my computer is in UEFI mode (which I wish to retain).

I spent a lot of time getting my present Win7 OS fully installed, updated and configured and would be unhappy if I need to start over reinstalling after the conversion. Is there a non-destructive method to do such a conversion so that my present Windows 10 on the first partition is still bootable?

I have a good Acronis backup of the Win 10 OS on this disk. Alternatively, would it work to delete all partitions, convert the MBR disk to GPT, then restore the OS from my backup? Or is it not possible to restore a bootable OS backup from an MBR disk to a GPT disk because of partitioning issues having to do with possibly different ways that boot sectors are handled in MBR and GPT?

 

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Hello Menomena,

While there is no 1-step MBR to GPT conversion option for your case, you can still apply the alternative solution that you have described. Steps would be as follows:

1) boot the computer from Acronis bootable media, start Acronis True Image

2) click on Tools & Utilities tab, then on "Add new disk"

3) select your system disk and proceed, intitializing it as GPT. Upon initialization everything on that disk will be deleted, disk will become emtpy with only "Unallocated space" on it. You do not need to create any partition manually.

4) click on "Recovery" tab in bootable media and restore your system from backup to the cleaned system GPT disk.

See http://www.acronis.com/en-us/support/documentation/ATI2016/index.html#26852.html for more details.

Regards,

Slava

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No need to  "Add new disk". Boot from the rescue media in UEFI mode is enough.

http://www.acronis.com/en-us/support/documentation/ATI2016/index.html#26852.html

I successfully converted my mbr NVme M2 disk to gpt with this method.

 

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Hasan, thank you for taking the time to share your experience here!