Is Clean command needed, convert MBR partition to GPT with Diskpart?

[Anthony Indiana]

Good Day,

I was installing Windows 7 Pro, 64 bit on my desktop computer. I tried several times, and kept running into this error message:

Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks.

I looked at several You Tube videos on how to convert a partition from MBR to GPT using Diskpart. They all used the clean command, which erases * EVERYTHING * on the hard drive. Sure, I have 2 backups of everything on that drive, but I would rather not reinstall everything for no reason.

The question - is it necessary to use the clean command when using Diskpart to convert a partition from MBR to GPT? Why not just leave all the files alone?

Also, it was annoying that not one of those people mentioned - Oh, by the way, this clean command will erase every single file on your hard drive! Did you back up your stuff?

I skipped Diskpart, and used Aomei Partition Manager to make the conversion. But I want to make my own video, for people who are not super nerds, and dealing with the same error message.

Problem 2: Converting the partition from MBR to GPT did me no good at all! I kept trying various things, and still running into error messages. After 4 hours of this nonsense, I came across a video about making an EFI partition. I was wondering, maybe with a GPT partition Windows needs it's own partition, it's own special safe space.

Oh frabjous day, that was the answer! Once you switch to GPT, Windows needs its own partition of at least 100 megabytes. It was super annoying that out of all the articles I read and videos I watched, not one person mentioned this obvious and essential fact!

So that's why I want to make my own video, to explain how to deal with this error message, and include all the important parts that the other guys left out.

Thank you much for you insights.

 

[Snick]

Hi Anthony,

Welcome to Sevenforums!

I don't use diskpart for this and other reasons. The Windows built-in Diskpart Command can only convert MBR to GPT by cleaning the disk first, which will lead to a great data loss.

I use EaseUS Partition Master Free. Or AOMEI Partition Assistant Free.
You can convert MBR to GPT or GPT to MBR, no formatting or erasing disk.

Googled mbr gpt explained

Some basics of MBR v/s GPT and BIOS v/s UEFI - Manjaro Wiki

What's the Difference Between GPT and MBR When Partitioning

Briefly MBR vs GPT | What are the main differences between ...

Videos

MBR and GPT Partition Tables - YouTube

UEFI vs Legacy BIOS Boot | GPT vs MBR (DOS) | Explained ...

Snick

 

[Megahertz07]

You're mixing concepts.
- A drive standard for the layout of partition tables can be GPT or MBR type.
- Boot systems can be Legacy - MBR or UEFI - GPT

You can easily convert a MBR drive to GPT and from GPT to MBR changing the layout of partition tables.
But to convert a Legacy - MBR boot able drive to a UEFI - GPT boot able drive it needs more than just convert a MBR drive to GPT changing the layout of partition tables.

A UEFI - GPT boot able drive requires:
- The computer must have a UEFI BIOS.
- The OS must be 64 bits.
- The drive must be GPT with a Fat32 partition with the boot loader (must be created on the conversion)

Win 10 and Win 10 installation drive has a tool (mbr2gpt.exe) that can convert a Windows Legacy- MBR boot able drive into a UEFI - GPT boot able drive. It was created for Win 10 conversion but also works on Win 7.

ALWAYS backup your drive before you do anything.

Boot from Win 10 installation drive, launch a CMD window and type:
Diskpart (to enter diskpart)
List disk (take note from the win 7 disk you want to convert)
exit (to exit diskpart)
MBR2GPT /convert /disk:<diskNumber>

Brink tutorial Convert Windows Legacy-MBR to UEFI-GPT without data loss

 

[SIW2]

That is odd. Aomei creates an esp partition when converting mbr>gpt.

Not sure what you did wrong.

 

[BrainDamage]

If the disk is full (fully partitioned), there's no space to put the EFI partition. I also think the EFI partition needs to be the first partition in physical order, but less sure about that.

You could've saved yourself the trouble by flipping the IDE/AHCI switch in your BIOS to IDE (sometimes called Legacy mode). If you boot the Windows 7 install drive in AHCI mode, it will only want to install to an EFI system. (Some very new mobos don't do IDE anymore, but they probably also won't run a vanilla Win7 install disc.)

 

[Megahertz07]

If the disk is full (fully partitioned), there's no space to put the EFI partition. I also think the EFI partition needs to be the first partition in physical order, but less sure about that.

You could've saved yourself the trouble by flipping the IDE/AHCI switch in your BIOS to IDE (sometimes called Legacy mode). If you boot the Windows 7 install drive in AHCI mode, it will only want to install to an EFI system. (Some very new mobos don't do IDE anymore, but they probably also won't run a vanilla Win7 install disc.)

You're mixing things. IDE/AHCI has nothing to do with the type of the disk (MBR / GPT) or the way you want to boot (Legacy - MBR or UEFI - GPT).

 

[BrainDamage]

As I said if you boot Windows setup disc in UEFI mode it won't install to an MBR-formatted disk. "UEFI mode" is also called "AHCI" or "SATA" in many BIOSes (or "many UEFIs" if you want to make it more confusing). Of course the terminology is all wrong and this is conflating two switches and giving them a third name (nobody even has IDE disks anymore?), but don't shoot the messenger

This setup quirk may have been fixed in setup discs newer than mine, but clearly this is the problem OP ran into. Win 7x64 will install to non-EFI (non-GPT, that is MBR) disks at least when "Legacy" (aka "IDE") mode is turned on. It's less of a hassle to flip a bit in BIOS (if the BIOS has the bit) than to repartition the disk.

 

[Anthony Indiana]

Will Easeus Partition Master Free convert a bootable drive MBR to GPT?

Snick, I read the articles and watched the videos.

With Easeus Partition Master Free, can I convert a * system * hard drive from MBR to GPT, without losing files on the hard drive? Or maybe I should say a bootable hard drive. (There is nothing on the hard drive that I want to keep. I just want to know if it's possible.)

I tried this with Aomei Partition Assistant Free, but I discovered the free version of Aomei will only convert data drives from MBR to GPT. To convert a system hard drive from MBR to GPT, I have to pony up and pay for the professional edition.

I connected the drive to my working computer with a little hard drive adapter cable. Then I used Aomei to change it from MBR to GPT. When I tried to install Windows 7, I just got an error message.

I'm wondering if this will work with Easeus Partition Master Free.

Thank you much for your help!

Megahertz07, I am trying to install Windows 7. You're on the Windows 7 forum. That MBR2GPT command is only available in later versions of Windows 10.

 

[SIW2]

Anthony Indiana


AOMEI PART ASSIST PRO


HOW TO CONVERT TO GPT WITH DISKGENIUS

 

[Snick]

Snick, I read the articles and watched the videos.

With Easeus Partition Master Free, can I convert a * system * hard drive from MBR to GPT, without losing files on the hard drive? Or maybe I should say a bootable hard drive. (There is nothing on the hard drive that I want to keep. I just want to know if it's possible.)

I'm wondering if this will work with Easeus Partition Master Free.

Thank you much for your help!

Yes, I do it all the time, MBR>GPT GPT>MBR That is why I suggested it. I never recommend an app without knowing about how it works. If I research an OP's issue & I'm not familiar with an app or a set of instructions, if I can, I test it on my test drive.

Google is well my friend. here you go from EaseUS
Free Convert MBR to GPT Without Data Loss - EaseUS
Change GPT Disk to MBR Disk Without Formatting - EaseUS

Question: Have you ever tried to shrink a Windows partition on a drive with Disk Management?

Quite often you can't shrink it much due to unmovable files at the end or near the end of the partition. If you simply download and try a partition resizing program, and you just resize the Win partition, it will most probably trash your OS because the program does not take into consideration those files exist.

Disk Perfect is what I use. It does recognize those files, saves and moves them to the end or near the end of the resized partition. Works for me, every time I've used it. If you install the trial paid version I believe. To remove the trial cookie, run Revo Uninstaller and you can do that again and again.!

Snick

 

[Snick]

What is ESP?

The EFI system partition (ESP) is a partition on a data storage device (usually a hard disk drive or solid-state drive) that is used by computers adhering to the Unified Extensible Firmware Interface (UEFI). What that means is that the EFI Partition is an interface for the computer to boot windows off of.

 

[Megahertz07]

Megahertz07, I am trying to install Windows 7. You're on the Windows 7 forum. That MBR2GPT command is only available in later versions of Windows 10.

I know you're trying to install Win 7.
If you carefully read my post #3 you will see that I mention that with a Win 10 installation disk you can use mbr2gpt tool to convert a Win 7 Legacy-MBR drive into a Win 7 UEFI-GPT drive.