By Emily / Last Updated April 27, 2023

Why change Legacy to UEFI?

UEFI vs BIOS

Legacy and UEFI are two firmware interfaces for computers. They work like an interpreter between the OS and platform firmware. When you boot up a computer, the interface (Legacy or UEFI) will initialize the hardware components and start the OS installed on the disk. But many users wonder what's the difference, or which one is worth using over the other one. On the whole, UEFI is better than Legacy BIOS with the following advantages:

● Legacy BIOS uses the MBR disk while UEFI uses the GPT hard drive. The major difference between those two partition styles is that MBR can only support up to 2TB hard drive while GPT can support up to  9.4ZB, which dramatically breaks out the 2TB disk size limit.
UEFI can enhance the boot time and elevate the computer speed, which will make a big difference when you install a large hard drive in your device.
Compared with BIOS, the UEFI comes with the Secure Boot feature. It can make the boot process much more secure by preventing the UEFI drivers or OS boot loaders without an acceptable digital signature from loading.

So,  it is easy to conclude that the UEFI performs the same job as Legacy, but does better. Changing BIOS mode from Legacy to UEFI can be a bit of upgrade and worth doing if you are using 64-bit Windows 7/8/8.1/10/11. By the way, Microsoft proclaims that upgrading from Windows 10 to Windows 11 also requires the UEFI boot mode and GPT partition table.

Is it necessary to reinstall Windows for Legacy to UEFI switch?

As mentioned above, the Legacy requires that Windows boots from an MBR disk and UEFI require a GPT boot disk, so it is necessary to convert MBR to GPT when switching the firmware setting from Legacy to UEFI. Meanwhile, you will lose everything including the operating system on the target disk during converting the disk from MBR to GPT. So, normally, it is necessary to reinstall Windows for changing to UEFI mode. If you want to convert Legacy to UEFI, detailed steps are listed as follows:

1. After you convert Legacy BIOS to UEFI boot mode, you can boot your computer from a Windows installation disk.

2. At the Windows Setup screen, press Shift + F10 to open a command prompt.

3. Type “diskpart” and use the command “list disk-> select disk #-> clean->convert gpt” to convert the disk from MBR to GPT as in the screenshot below:

Convert to GPT

4. Now, you can go back and reinstall Windows. If you try to install Windows without these steps, you will get the error “Windows cannot be installed to this disk” after you change BIOS to UEFI mode.

★Tip:
The "clean" command is required to delete all partitions on the disk because the command prompt can only convert an empty disk.

How to change Legacy to UEFI without reinstalling Windows or losing data?

With the first traditional method, it is inevitable to reinstall OS. So, many users feel confused about whether they can convert MBR to GPT without deleting data and switch Legacy to UEFI without reinstalling Windows 11, 10, 8, and 7. Luckily, there are some professional and safe tools like AOMEI Partition Assistant Professional Edition, allowing you to convert the disk from MBR to GPT without deleting partitions or losing data in Windows 11/10/8/7 and Windows XP/Vista (convert MBR and GPT without data loss in Server operating systems, the Server edition can satisfy you). This way, you don’t need to spend time reinstalling Windows and all of your programs for enabling UEFI boot mode.

Download Pro Demo Win 11/10/8.1/8/7/XP
Secure Download

Note: To avoid data loss caused by improper operation or some accidents like power outages, you can back up vital data beforehand.

Please download the Demo version to see how to change Legacy to UEFI:

1. First, download and run AOMEI Partition Assistant Pro.

2. Right-click on the system disk and select Convert to GPT or click the disk and choose Convert to GPT from the right column.

Convert System Disk to GPT

3. Click "OK" to continue your operation.

OK

4. Click “Apply” > "Proceed" to apply the change.

Apply to GPT System Disk

During the process, your computer will reboot into AOMEI Pre-OS mode. When it completes, you can go into the BIOS and switch from Legacy to UEFI mode. You can use the same method to convert GPT to MBR without losing data.

How to change BIOS mode from Legacy to UEFI Windows 10

The steps to turn on UEFI mode vary from computer to computer. You can refer to the following to help you configure yours.

1. Typically, you continuously press a specific key when the computer starts up to enter the EFI Setup menu. Normally, it is Del for desktops and F2 for laptops. If you don’t know which key to press, just press Esc. It will give you the full menu, and then you can select BIOS Setup.

2. Normally, you can find the Legacy/UEFI boot mode configuration under the Boot tab. Under the Boot tab, you should disable Legacy and enable UEFI.

BIOS UEFI

3. Now, press F10 to save the settings and then exit.

In conclusion, it is recommended that you change Legacy to UEFI boot mode if your operating system (OS) is compatible. As you can see, the entire process doesn’t take much time or effort since as you don’t need to reinstall Windows 11,10, 8, and 7.