Background on MBR and GPT Disk
MBR – Master Boot Record: MBR is a guide sector at the very front of the drive, the concept for which originated in 1983 with the partitioning of disks for IBM compatible personal computers. MBR describes the information on logical partitions, containing file systems and the organization type. MBR contains the boot routine – this is the executable code produced when computer loads the operating system in the second stage of the start-up or the boot record which connects every partition (VBR).
Note: MBR cannot be created on media which cannot be partitioned – such as CDs/DVDs.
GPT – GUID (Globally Unique Identifiers) Partition Table: GPT has become the new standard of disk partition table originating from the EFI (Extensive Firmware Interface). When compared to MBR, GPT is a much more flexible disk partition.
What are the limitations of an MBR disk?
MBR disks only support partitions up to 2TBs in size and will only allow four primary partitions. If the partitions surpasses 2TBs in size the additional space will show as unallocated space.
MBR partitioning rules are complex and poorly designed.
What are the advantages of a GPT disk?
1. It can take full advantage of a hard drives capacity and surpass the 2TB limit set by MBR.
2. GPT disks allows for an almost unlimited number of partitions, Windows however restricts this number to 128.
3. When compared to MBR you can have more primary partitions. Each GPT partition has a unique identification GUID and a partition content type.
4. Where MBR limits the partition size to 2TB, GPT doesn’t have a limit. When using Windows, the partition size is limited to 256TB as each partition in GPT can be up to 2^64 logical blocks in length.
5. A Partition on a GPT disk has self-contained backup which is stored at the end of the disk, with the original being stored at the front of the disk. When one of the two is destroyed, you can restore it with the other.
What to do when you need to convert between MBR and GPT Disks?
As we mentioned before, MBR disks can only support partitions up to 2TBs in size. If you have a disk which is MBR formatted and larger than 2TB, you can only use 2TBs of the capacity, the rest can’t be used. It is necessary to convert the MBR disk to GPT in order to take full advantage of the capacity over 2TBs.
Unfortunately, Windows 95/98/ME, Windows NT4, Windows 2000, Windows 2003 32-bit, and Windows XP 32-bit version do not support GPT partitions. GPT disk will therefore display as a ‘GPT protective partition’ in these systems and you won’t be able to access your data unless you convert the drive back to MBR.
Note: If you want to convert a disk larger than 2TB GPT disk back to an MBR disk, you should be aware that any data above 2TB will be lost. If you still wish to convert your GPT drive to MBR you can transfer the extra data before the conversion to another drive via this helpful data migration software.
How to convert a disk between GPT and MBR without affecting the OS?
First, you can use convert GPT to MBR or MBR to disk without data loss, you can apply AOMEI Partition Assistant Professional in order to convert GPT to MBR without data loss. Let’s see how it works below.
Step 1. Install and launch AOMEI Partition Assistant Professional Edition. Select the data disk you want to convert and right click it, and then select "Convert to GPT Disk" (or “Convert to MBR Disk”) in the drop-down menu.
PS: If you are working with Windows Server, you can use AOMEI Partitioni Asssitant Server or Advanced Edition.
Step 2. Click "OK" after confirming the operation.
Step 3. You can preview the conversion under “Pending Operations”. In order to save the changes, please click “Apply” on the toolbar and wait for the process to be completed.
How to convert GPT to MBR without an operating system?
When installing Windows 10, 8, and 7, you may get an error message saying that Windows can’t be installed on this disk: The selected disk has an MBR partition table or GPT partition table. If this is the case, you can convert the disk from MBR to GPT (or vice versa) which will allow you to install Windows. You can use a USB flash drive or CD to create an AOMEI Partition Assistant bootable media which will allow you convert between MBR/GPT without any data loss.
Refer to the steps listed below:
Step 1. Insert an USB flash drive or CD into another working computer running Windows 10, 8, and 7 and launch AOMEI Partition Assistant.
Step 2. Click on "Make Bootable Media "and follow the wizard to finish creating a bootable media drive/disk.
Step 3. Insert the bootable drive/disk into the computer that you’re having problem installing Windows on, and then boot from the bootable media drive/disk.
Step 4. When AOMEI Partition Assistant is loaded, you can successfully convert the hard drive to MBR or GPT.
Once you have changed the disks format you should be able to install Windows on this disk. If you are not worried about data loss you can follow the instructions here in convert MBR to GPT with DiskPart utility.
When converting between MBR or GPT on laptops you should make sure the laptop has sufficient power supply by connecting it to the power outlet.
In order to protect your data, you must not terminate the program during the conversion process.