How to Convert MBR HDD to GPT Without Data Loss

hard drivembrpartitioningwindows

I tried to install a windows 10 DVD on my laptop with windows OS, after formatting the OS drive, I got the "MBR drive" error, so I should convert it to GPT, but I have no OS on laptop, and there is the other two drives D, and E, which I don't want to erase.

I know I can convert it by "AOMEI Partition Assistant" but I couldn't get it to work on an old XP / Win7 live disk I have.

EDIT:

the error I get:

Windows cannot be installed on this disk. The selected disk is of the GPT Partition style.

In my Lenovo G50 's bios there is these boot options:

Boot Mode: Legacy Support => UEFI First / Legacy First => USB Mode: ON/ OFF

Boot Mode: UEFI => USB Mode: ON/ OFF

Edit2

I did test Windows 8, 7 and XP, same error.
I tried a Live disk with some partitioning application on it, but it couldn't do the trick w/o data loss.

Best Answer

If you prefer to keep your hard drive the way it is, you can disable Secure Boot on your motherboard, then try installing windows the same way you did. It should work without needing to convert to GPT. If you prefer to convert your hard drive, this question has already been answered elsewhere.

The reason why Windows refuses to install on a MBR drive is because Secure Boot is enabled on your motherboard. When Secure Boot is enabled, any software that is set to boot must be signed by a Certificate Authority in order for the motherboard to authorize it. That includes the installation media and the operating system once installed.

The error occurs because the Windows installation detects it is being ran through Secure Boot and knows it must require to be installed on a Secure Boot compatible hard drive, which is GPT. Once the installation is done, the motherboard boots from the Windows partition but only after Secure Boot verifies the signature of the operating system on that partition.

Motherboard type = BIOS and EFI
BIOS uses MBR.
EFI uses MBR and GPT.
Secure Boot which is a feature of EFI can only be used with GPT.

Enabling CSM on a motherboard is basically running the motherboard as a standard BIOS motherboard, thus disabling Secure Boot.

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