By AOMEI / Last Updated November 30, 2020

UEFI is the replacement for BIOS

All new hardware nowadays uses the unified extensible firmware interface (UEFI) instead of the traditional BIOS. UEFI is now well on its way to replacing BIOS which by now is an outdated standard, well over 40 years old! At present, most UEFI enabled systems have a Legacy boot mode in order to be compatible with older systems.

If you are using Windows 7 64-bit, Windows 8/8.1, or Windows 10, you can change Legacy to UEFI mode to get better performance and disk support. In Legacy mode, Windows can only boot from master boot record (MBR) disk that has 2TB size limit while UEFI mode works with GUID partition table that allows you to use disks of enormous size.

Is it necessary to reinstall Windows 10/8/7 for UEFI mode?

Normally, you need to reinstall Windows for changing to UEFI mode because you need to wipe the hard drive and then convert to GPT disk.

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

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

3. Type “diskpart” and use command “convert gpt” to convert the disk from MBR to GPT as the screenshot below.

Convert GPT

4. Now, you can go back and install 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.

Seems complicated right? There’s actually an easier way that involves far less messing around in Command Prompt. You can use specialist third party software AOMEI Partition Assistant Professional Edition to convert from MBR to GPT without deleting partitions or losing data in Windows 10/8/7 and Windows XP/Vista (convert MBR and GPT withou data loss in Server operating systems, the Server edition can satifsy you). This way, you don’t need to spend time installing Windows and all of your programs or typing out a string of command prompt commands.

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

To convert to GPT disk with AOMEI Partition Assistant Professional:

1. Download this partition manager software Demo Version and run it.

2. Right click on the system disk and select Convert to GPT Disk.

Convert System Disk to GPT

3. Click “Apply” 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 Legacy to UEFI?

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.


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 10, 8, and 7.