How can I install w10 in uefi mode

Hi guys, I made a mess installing w10 in legacy bios mode, while I saw already running w8 in uefi mode.
I'm actually on a w10 system with legacy bios mode.
How can I install w10 in uefi mode, if bios won't start the installation of w10 using an usb with iso of w10 mounted in uefi gpt mode?
Thank you

There is a way you can do this by creating a system image of your legacy bios mode and restoring it to a UEFI/GPT mode. The procedure is well documented in Macrium Reflect which is a free tool for making system image backups and often recommended on this forum.

There is a way you can do this by creating a system image of your legacy bios mode and restoring it to a UEFI/GPT mode. The procedure is well documented in Macrium Reflect which is a free tool for making system image backups and often recommended on this forum.

I am amazed that Macrium put this article in their knowledge base. With this procedure, Windows will work and boot using UEFI mode. However, the partition scheme is incorrect.

A normal, fresh install of Windows 10 will have 4partitions, not 3:

1. 450MB Recovery partition (Tools for trouble shooting, Reset, Refresh, diagnistics ...)
2. 100MB EFI FAT32 System partition (Boot code. Without it, Windows won't boot)
3. 16MB MSR (Microsoft Reserved partition for use with GPT disk type)
4. C Drive

As you can see. #1 was ommited by the article. That means there's no way to create a Recovery disk. In addtition, The sizes of EFI and MSR partitions are wrong.

To get the correct partition scheme. Follow the procedure in this link:
Solved Help With Partition Management - Windows 10 blog

Hi guys, I made a mess installing w10 in legacy bios mode, while I saw already running w8 in uefi mode.
I'm actually on a w10 system with legacy bios mode.
How can I install w10 in uefi mode, if bios won't start the installation of w10 using an usb with iso of w10 mounted in uefi gpt mode?
Thank you

Sounds like you usb stick is not correctly created, or pc is not set to eufi mode.

You have to download iso, and burn to usb stick, using rufus specifically selecting it is for a gpt eufi install (loasds of web guides).

Then you have to make sure bios is set to eufi mode, and boot from usb stick, and select custom install, deleting all partitions first.

To create a UEFI USB Installation Drive using Rufus, Use Option 2, #6. USB Flash Drive - Create to Install Windows 10

For the clean install, Windows 10 - Clean Install

Isn't it simpler just to use the Media Creation Tool to create a bootable USB Windows 10 installation drive? See Option 1 at USB Flash Drive - Create to Install Windows 10

Isn't it simpler just to use the Media Creation Tool to create a bootable USB Windows 10 installation drive? See Option 1 at USB Flash Drive - Create to Install Windows 10

Normally I would agree but some people have found if they create a usb stick that way on a legacy bios machine, it does not work properly when you switch pc to eufi mode and try a eufi install.

That is why I suggest RUFUS and GPT mode specifically here to ensure that is not an iissue.

Hi guys, I made a mess installing w10 in legacy bios mode, while I saw already running w8 in uefi mode.
I'm actually on a w10 system with legacy bios mode.
How can I install w10 in uefi mode, if bios won't start the installation of w10 using an usb with iso of w10 mounted in uefi gpt mode?

Do you know how to choose the Legacy BIOS or UEFI boot mode?

Depending how the Windows install media is booted (Legacy BIOS or UEFI) Windows creates either MBR or GPT partition table on the SSD/HDD.

- The non-UEFI option will boot the Windows install media in the Legacy BIOS mode and Windows Setup will create the MBR partition table automatically.
- The UEFI option will boot the Windows install media in the UEFI mode and Windows Setup will create the GPT partition table automatically.

Here are two examples of the one-time boot menu.

I had problems installing Win 10 from a USB stick until I changed the SATA option from AHCI to ATA.

Try it again in AHCI, just disconnect all drives you are not installing Windows on before you start up. What error did you receive?