By AOMEI / Last Updated October 14, 2019

There are three kinds of BIOS boot modes: Legacy, UEFI, and Legacy+ UEFI. Read this post and you’ll realize how to select proper boot mode under different situations.

Legacy boot mode

Legacy boot mode, as its name implies, is a kind of traditional boot mode. It is common in Windows systems before Windows 8. It owns good compatibility and can be used on both on 32bit and 64bit systems.

Legacy boot mode supports MBR disk, whose features are listed as follows:

  • It supports up to four primary partitions.

  • It doesn’t support a disk beyond 2TB.

  • Only one operating system boot record can be stored in a single MBR.

UEFI boot mode

UEFI, the successor to Legacy, is currently the mainstream boot mode. Compared with Legacy, UEFI has better programmability, greater scalability, higher performance and higher security. Windows system supports UEFI from Windows 7 and Windows 8 starts to use UEFI by default.

UEFI supports GPT disk, which owns the following features:

  • It supports up to 128 primary partitions.

  • It breaks disk size limitation of 2TB and supports up to 18EB.

  • UEFI offers secure boot to prevent various from loading when booting.

  • The interface of UEFI BIOS is more intuitive, more interactive and it supports mouse operation and multi-language.

  • There is no self-test process at boot time and the boot speed can be faster.

Legacy Uefi

Legacy+UEFI boot mode

Legacy mode is old but not completely useless, as some hardware (like GTX660) and systems (like XP) only support Legacy mode.

Legacy And Uefi

Therefore, most new motherboards also allow users to switch to Legacy+UEFI compatibility mode. When the BIOS detects a system installed under Legacy, it will start the Legacy boot mode. Similarly, if it detects a system installed under UEFI, It will start in UEFI mode.

How to check out boot mode?

Click Start button and go to All Apps> Windows Administrative Tools > System Information> BIOS Mode

Windows Adminstrative Tool

System Information 1

How to make conversion between MBR and GPT without data loss?

Considering that the combination of GPT and UEFI is the most reasonable or downgrade installation of 32bit Windows 7 or XP, you can convert your disk at first. Here introduces you how to make conversion between MBR and GPT without losing data via an effective tool – AOMEI Partition Assistant Professional.

Note: To avoid data loss caused by wrong operation, you can back up your data via AOMEI Backupper Standard.

Step 1. Install and run AOMEI Partition Assistant Professional. In the main interface, right click the disk that you need to convert and choose Convert to GPT Disk.

Convert System Disk To Gpt

PS.: If your disk is originally initialized as GPT, you’ll see Convert to MBR option. You can choose it to convert GPT disk into MBR without losing data.

Step 2. Click OK and Yes to confirm your operation.

Ok To Gpt System Disk

Step 3. You’ll get back to the main interface. Click Apply and Proceed to commit the operation.

Apply To Gpt System Disk

Notice: Make sure that your motherboard supports UEFI before converting system disk into GPT; ensure that the motherboard supports Legacy before system disk converting to MBR. If the motherboard doesn’t support according boot mode, you can enter Windows after conversion. You can enter BIOS to check whether the motherboard supports the corresponding boot mode.


UEFI is a new boot mode and it is usually used on the 64bit systems later than Windows 7; Legacy is a traditional boot mode, which supports 32bit and 64bit systems. Legacy + UEFI boot mode can take care of the two boot modes.

UEFI is better than Legacy in many aspects and is promoted by major software and hardware vendors.