Windows 10: How do I change my BIOS back to UEFI?

My OS disappeared overnight. Was working fine the day before.I didn't mind as I needed an upgrade anyway. I changed the BIOS from UEFI to Legacy in an attempt to install a new Windows and I can't change the BIOS back to UEFI. The option is not there. I've reset to defaults with no luck. I have an ASUS P8P67.

:)

 

Changed to gpt and uefi bios, now windows wont boot

Emil Gyldenskog Nøsavik

Thank you for posting in the Microsoft community.

When a MBR hard disk is converted to GPT, if you can't get into the system, it's usually due to incorrect BIOS settings or no UEFI boot. Here are the steps to solve this problem:

1. Enter PE system: Use a USB flash drive to boot and enter the PE system (pre-installation environment) to make sure the data is normal.
   
2. Check the BIOS settings:
   
   • Make sure UEFI boot is set in BIOS.
     
   • If the BIOS is set to UEFI boot, but the partition is still MBR partition, you need to modify the BIOS settings to match the hard disk partition mode and boot mode.
     
3. Use a PE tool that supports UEFI: Make sure the PE tool you use supports UEFI repair boot.
   
4. Create an EFI system partition:
   
   • In PE system, open "Disk Management", find the SSD (usually labeled as "Disk 1"), right-click and select "Compress Volume" to compress about 500MB of space.
     
   • Open a command prompt, type `diskpart` and enter.
     
   • Use the `select disk` command to select the SSD.
     
   • Use the `create partition efi` command to create the EFI system partition.
     
   • Format the EFI partition using the `format fs=fat quick` command.
     
   • Use the `assign` command to assign a drive letter to the EFI partition.
     
5. Bootstrap Repair:
   
   • In a command prompt window, type `bcdboot x:\windows /s y: /f uefi`, where `x` is the drive letter where the system is located in the SSD and `y` is the drive letter of the EFI partition.
     

Hope the above information can help you



Best Wish

Shawn Z | Microsoft Community Support Specialist

 

Should I change BIOS Mode to UEFI?

You boot into UEFI mode by disabling CSM mode (or possibly called legacy mode) in your UEFI settings. But, until you prepare your hard drive (or SSD) to boot in UEFI, you likely will fail to boot. To convert your HDD or SSD to boot in UEFI mode you could try this:
Convert Windows 10 from Legacy BIOS to UEFI without Data Loss

But, if you succeed in converting the HDD/SSD to GPT, and you can't change you BIOS to boot in UEFI mode, then again you will fail to boot. So, I would suggest that you really know what you are doing before you undertake changing legacy BIOS (CSM mode) booting to UEFI.

I would suggest running Ubuntu in a Virtual Machine rather than dual booting.

 

bios

Hi all i am new in this forum, i need meanings step by step of each item listed in the bios Phoenix-Award