My pc will not boot into windows after i change from CSM to UEFI.

Hello oli Aston1,

Welcome to Microsoft Community.

This is because your computer is using a traditional boot mode. In the BIOS, the computer is booted in CSM compatible mode by default, so when you change to UEFI boot, the computer cannot detect the boot disk and will not boot to Windows.

The fix is actually very simple, just restore the changes you have made in the BIOS, and the most important thing is to turn CSM back on. Only then can your boot disk be recognized by the computer.

Rest assured that these actions will not affect any data on your computer.

Best regards,

Mitchell - | Microsoft community support expert from MSFT

How do I make it so my computer will boot with UEFI to enable secure boot.

Hi oli Aston1,

This involves how the system is installed and whether your motherboard supports this feature.

The first thing you need to know is, Master Boot Record (MBR) disks use the standard BIOS partition table. GUID partition table (GPT) disks use the Unified Extensible Firmware Interface (UEFI).

On most Windows 10 computers, the MBR disk format is used, and MBR corresponds to BIOS, so if you want to boot your computer with UEFI and enable secure boot, you can try converting Windows 10 from MBR to GPT partition table with mbr2gpt:

MBR2GPT - Windows Deployment | Microsoft Learn

If you have done the above, then after restarting your computer, you will be able to disable CSM (Compatibility Support Module) in the BIOS and start UEFI secure boot.

However, let me kindly remind you that this operation is risky, and if you plan to do this, please back up all important data in advance to prevent loss.

In addition, if you find that you cannot convert the disk format with mbr2gpt, then I recommend that you reinstall the system after fully backing up all the data. During installation, format the disk format to GPT.

Best Regards,

Mitchell | Microsoft Community Support Specialist 

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