Windows – Install Windows 7 on mbr hard disk with UEFi firmware

gptmbruefiwindows 7

I have a Toshiba and I want to install Windows 7 on it. My firmware is UEFI. I have disabled the secure boot and I have enabled the Legacy support.Before the installation of Windows 7 i have partitioned my hard disk with MBR with gparted.

I then try to install Windows on it. The problem is that Windows during the installation converts my hard disk to GPT automatically. Why? How can i solve this problem?

Best Answer

From UEFI Wikipedia page:

To ensure backward compatibility, most UEFI firmware implementations on PC-class machines also support booting in legacy BIOS mode from MBR-partitioned disks, through the Compatibility Support Module (CSM) that provides legacy BIOS compatibility. In this scenario, booting is performed in the same way as on legacy BIOS-based systems, by ignoring the partition table and relying on the content of a boot sector.

BIOS-style booting from MBR-partitioned disks is commonly called BIOS-MBR, regardless of it being performed on UEFI or legacy BIOS-based systems.

Furthermore, booting legacy BIOS-based systems from GPT disks is also possible, and such a boot scheme is commonly called BIOS-GPT.

  • Windows installation booted from EFI, does not allow installation on MBR disks and vice versa.

  • EFI installation needs EFI partition scheme TO BOOT (correct me if I'm wrong)

like:

Partition   FileSystem   Size   Purpose

EFI         FAT32        100MB  EFI Boot Sector on GPT disk
MSR         N/A          128MB  Hidden Services Partition for GPT disk
Primary     NTFS         N/A    Windows Installation/Data Volume contaning VHD

But, it can load windows from another MBR disk (or VHD) in CSM mode. So, to accomplish this, you need at least 2 disks, or 1 physical GPT disk, containing a Virtual MBR disk.

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