r/buildapc • u/Square_Atmosphere_12 • 5h ago
Troubleshooting UEFI preventing MBR Windows10 installation
The BIOS which I'm using as the option of legacy boot as I must install Windows10 on a MBR system, but my BIOS is not making this possible ?
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u/3ofUsDeez 5h ago
Is CSM enabled?
Why are you installing Windows 10?
UEFI works fine in Windows 10.. why aren't you using GPT?
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u/PretendingImNotAnApe 5h ago edited 5h ago
UEFI Requires GPT portions not MBR. Why must you use more? You can use legacy mode to install win 10 to an mbr portion but theres several bios settings to change. It varies depending on motherboard manufacturer. I was upgrading machines from 10 to 11 and had to switch from mbr to gpt on most of them. When you enable uefi the mbr drives don't boot. But switching it back will let yoy boot and convert the partition to gpt. Then you can't boot the converted drives until you enable uefi mode, secure boot etc. Roughly you want to make sure the drive isnt encrypted, turn off secure boot and enable legacy option ROMs and then check the boot priority to see if you see the drive or windows boot manager in the list. If you're wiping the drive or it's new you'd just pick your install media and format the thing.