Use legacy boot mode in Windows 8.1

Butters

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I've been wondering if it's possible to use the legacy (Windows 7 and earlier) BIOS instead of UEFI in Windows 8.1. In my BIOS settings, there is an option to enable the legacy boot mode, but Windows won't boot whenever this is enabled (I get the message 'Operating System not found' instead). Is there any way to enable this?

NOTE: I am not talking about secure boot; I already have that disabled.

Thanks in advance.
 

My Computer

System One

  • OS
    Windows 8.1 Pro, Windows 7 Professional, Windows XP Professional
    Computer type
    Laptop
    System Manufacturer/Model
    Dell Inspiron 15 7537
    CPU
    Intel Core i7
    Memory
    8 GB
    Screen Resolution
    1920x1080
    Browser
    Pale Moon
    Antivirus
    None, but I do use Malwarebytes Pro
Also, I'm using a Dell Inspiron 15 laptop in case that matters.
 

My Computer

System One

  • OS
    Windows 8.1 Pro, Windows 7 Professional, Windows XP Professional
    Computer type
    Laptop
    System Manufacturer/Model
    Dell Inspiron 15 7537
    CPU
    Intel Core i7
    Memory
    8 GB
    Screen Resolution
    1920x1080
    Browser
    Pale Moon
    Antivirus
    None, but I do use Malwarebytes Pro
It is a Windows weirdness. It won't boot from a gpt partition unless you use efi.

If you want to use Bios, windows needs to be on an mbr partitioned disk.
 

My Computer

System One

  • OS
    7/8/ubuntu/Linux Deepin
    Computer type
    PC/Desktop
GPT>MBR is doable. Various partition mangers will do it.

You also need a primary partition marked active ( that can be the windows partition , separate one not required).
 

My Computer

System One

  • OS
    7/8/ubuntu/Linux Deepin
    Computer type
    PC/Desktop
Yes, you will have to turn on CSM "Compatibility Support Module" in the bios, however, Windows 8 is optimized to run more efficient in UEFI mode.

When you try to install Windows 8, did you delete all the partitions, then click new? Windows will create the necessary partitions on the hard drive. The partitions are needed to boot in a UEFI environment.

Partitions are as followed

Recovery
System
MSR Reserved
Primary

Install to the primary drive.

Plus you need secure boot on with Windows 8 installation.
 

My Computer

System One

  • OS
    Windows 8.1 Pro with Media Center
    Computer type
    PC/Desktop
    System Manufacturer/Model
    ASUS
    CPU
    Intel Core 2 Quad Q6600 2.40 ghz
    Motherboard
    ASUS P5K PRO
    Memory
    2 GB DDR2
    Graphics Card(s)
    PNY NVIDIA Geforce GT 630
    Browser
    Internet Explorer 11
    Antivirus
    Windows Defender
If Windows is installed in UEFI mode it definitely won't boot in legacy mode. It's not possible since under UEFI Windows uses a different type of bootloader. That's why it won't boot when legacy mode is enabled. The bios simply does not find the bootloader where it expects it.

If you want to run Windows in legacy mode you will have to reinstall Windows by booting the setup DVD in legacy mode.

Converting GPT to MBR partitions is possible though, just search the web for a program that can do it, there are a few out there. But make a backup of your important data before you try to convert your partitions.
 

My Computer

System One

  • OS
    Windows 8.1 Update 1
    Computer type
    PC/Desktop
    System Manufacturer/Model
    self built
    CPU
    AMD FX-8350
    Motherboard
    Gigabyte GA-990FXA-UD7 Rev. 3
    Memory
    16 GB
    Graphics Card(s)
    Zotac GTX 770 Amp 2 GB
    Browser
    Firefox
    Antivirus
    GDATA Internet Security
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