The Case
"Hi, experts! Recently I was planning to clone my system drive from GPT disk to
another MBR SSD. So I was wondering do I have to convert MBR SSD to GPT first of all?
Or you guys have any other great suggestions on how to migrate OS from GPT disk to
MBR SSD directly without changing disk style?”
Why migrate OS to MBR SSD from GPT disk?
Although GPT comes with some obvious advantages over MBR disk, like allowing you to
create up to 128 primary partitions, supporting over 2TB disks and more, some people
still want to migrate OS from GPT disk. As we know, SSD will offer smaller disk
capacity comparing to HDD of the same price.
Most computers operating systems are
installed on hard disk drives (HDD) which may be with large size and initialized to
GPT disk. The newly purchased SSD, due to prices factor, perhaps has less than 2TB
capacity and initialized to MBR disk. To experience better performance, faster
booting speed, and decreased programs loading time, users would like to migrate OS
to MBR SSD from GPT disk in Windows.
Software to clone OS from GPT to MBR SSD
When it comes to migrate or clone Windows system from one disk to the other, a
cloning software or system migration tool would be of great help, since you cannot
move OS directly using Windows built-in tools. AOMEI Partition Assistant
Professional is such program that has “Migrate OS to
SSD” feature, allowing you to migrate operating system to new hard disk or a
speedy new SSD without reinstalling everything.
This software comes with a clean and
user-friendly interface, making it quite easy to use, even for the computer novices.
And it works well on Windows 10, 8/8.1, 7, XP and Vista.
There is one more matter that worth to mention. Technically, GPT works well with
Extensible Firmware Interface (EFI) or the Unified EFI (UEFI). And MBR works with
older and simpler firmware Basic Input/Output System (BIOS). Therefore, after you
switch from GPT to MBR, do not forget to change boot mode at the same time.
How to migrate OS from GPT disk to MBR SSD?
In the first place, connect the MBR SSD to your computer. It can be connected via
external disk enclosure or USB-to-SATA cable. Install and run AOMEI Partition
Assistant. This tutorial will take migrating Windows 7 from GPT to MBR for
example.
Step 1. Click Migrate OS to SSD in the left Wizard
pane. A dialog states this operation information pops up later. Click Next to continue.

Step 2. Choose the SSD as the destination space. Remember to check
box “I want to delete all
partitions on this disk 2 to migrate system to the disk” and click Next.

Step 3. You’re allowed to resize the system partition before
migrating. The drive letter can be reassigned manually.

Step 4. There is a Note on how to boot OS from
destination disk maybe you want to bear in mind.

Step 5. You’ll see the virtual result of system migration. ClickApply > Proceed to execute the pending operations.

Step 6. Shut down your computer if the migration finishes. Press F2,
Del, F8 or other specific key to enter BIOS. You need to alter two settings here,
boot priority and boot mode. Change boot priority to cloned MBR SSD and switch from
UEFI to Legacy. Then press F10 to save change and exit.

Tips:
The destination MBR SSD will be overwritten. Backup files that matter a lot
to safe place beforehand.
This process needs to be completed in Windows restart mode.
By default, this program will copy only used section of the source disk to
target disk. So, you can also migrate OS from larger drive to smaller one as
long as the used part fits.
If the OS drive on GPT disk is larger than 2TB, the process will fail because
MBR disk supports less than 2TB storage. You can shrink
volume/partition first and then try again.
Summary
Only in five steps can you easily migrate Windows OS from GPT disk to MBR SSD with
the help of the powerful partition tool. As a matter of fact, except for switching
from GPT to MBR, this software allows you to transfer OS
from GPT to GPT disk as well. In addition, the conversion between MBR and
GPT in this tool makes it a great alternative
to GptGen.