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Published on 11.05.07 by Brent Trahan

Convert a MBR Disk to a GPT Disk

Learn how to convert a Master Boot Record (MBR) disk to a Globally Unique Identifier Partition Table (GPT) disk in Windows Vista.

Hard drives are getting larger. The amount of information people are saving is growing rapidly. If you have a very large music, picture, or video collection you might want to consider using GPT instead of MBR as your partitioning system.

MBR partitions have been around for a long time. The GPT disk partitioning system is new and only works in XP x64, Server 2003, Windows Vista, and Server 2008. GPT’s advantages over MBR are:

  • GPT can support up to 128 partitions. MBR can only support 4.
  • A GPT partition can theoretically be as large as 18,000,000 terabytes in size!
  • GPT uses primary and backup partition tables.

This guide shows you how to convert a brand new (empty) MBR style disk to a GPT disk.

Converting from MBR to GPT Disks

  1. Right-click Computer in the Start Menu and then select Manage.
  2. Select Disk Management in the left column.
  3. Right-click the MBR drive you want to convert to GPT and then click Convert to GPT Disk.

Note: If the drive isn’t empty or it contains partitions you can’t convert it to GPT.

Still need help? Ask your computer question now.

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18 Responses to “Convert a MBR Disk to a GPT Disk”

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  1. How do I setup a 5TB system on RAID 5 on a Server 2008 x64 bit Standard Edition system?

  2. RedFlameOut says:

    To answer Matthew Carter, if your RAID 5 volume is on a RAID controller and the RAID controller appears as SCSI to Windows, 2TB is the limit of MBR disks. You must use a GPT disk.

    I don’t have experience with 2008 on how to setup GPT disks. Note that GPT disks under 2003 are limited to data disks only. You can’t boot from it. On 2008, that may not be an issue any longer.

  3. deko says:

    The ability to slice up a disk into more than 4 partitions is nice, but who does this these days? The only time I see *any* partitioning on a Windows system is to keep logs or a page file isolated. Still, GPT is better because MBR is antiquated – especially with Solid State drives around the corner.

    I came across an article here – http://www.techotopia.com/index.php/Adding_New_GPT_and_MBR_Disks_to_Windows_Server_2008_Systems – that says “64-bit systems can only boot from GPT disks.” I’m currently booting a 64-bit Windows Server 2008 from an MBR disk, so I’m not sure why the author wrote this. If anyone has any thoughts on this please let me know.

    I use GPT for all other disks in the server. Interestingly, my JBOD disks (RocketRaid 3120 controller) would not format unless they used GPT.

    In regard to setting up a 5TB RAID 5 – that’s easy: use six 1TB drives.

    • Abraracourcix9 says:

      64 bits system, he meant “REAL” 64 bit system.
      Intel only makes the Itanium processor and indeed it
      can only boot off a GPT disk.

      ALL 32 bits systems with 64 bits EXTENTIONS called “x64”
      ie: Fake 64 bit OSes, are REQUIRED to boot off an MBR.
      It can use GPT as data disk if they have these 64 extentions,
      or Windows Server 2003 SP1 and over. Including Windows Server
      2008 (x64) they ALL require to boot from a MBR disk. Only the
      Itanium processor that uses EFI as console (equivalent of BIOS
      in the Pentium/Xeon/AMD etc world) can and must boot of a GPT.

      Do NOT mix a real 64 bit system with a x64 OS. Remember, the “x”
      in x64 stands for “extentions”. The instructions are still made
      for 32 bit processors, only some registers and a few special
      instructions differs to access more than 4GB of RAM.

      There are no magic there.


      • Mark N. says:

        What a load of nonsense.

        AMD64 (a.k.a. x86-64) processors and operating systems (Windows, OSX, Linux, etc.) are very much 64-bit. The reason why the industry uses “x64” is to distinguish the x86-64 (AMD64 / Intel64) instruction set from other 64-bit instruction sets (like IA64, zArchitecture, RS64, etc.). There are lots of different (and incompatible) 64-bit instruction sets, and Microsoft made versions of Windows for two of them (IA64 and x86-64). If they called them simply “64”, people woldn’t know what version they were buying.

        The “x” does not (and never did) stand for “extensions”. It was simply a way to refer to the processor family that included the 8086, 80286, 80386 and 80486 (i.e., they all ended in “86”), hence the generic name “x86”, and later “x86-64” (because Intel doesn’t want to admit they’re using a 64-bit instruction set created by AMD, so they’d never call it AMD64), often shortened to “x64”.

        Windows x64 is able to run 32-bit software (just as x86-32 versions are able to run 16-bit software) by using a built-in emulator, but most software companies now have native 64-bit versions of their software for x86-64 systems.

        Finally, the ability to boot from GPT (instead of MBR) depends on the motherboard’s BIOS, not on the OS. When the system starts booting the OS hasn’t been loaded yet, so it’s irrelevant. Lots of x86-64 systems use an EFI BIOS (ex., Apple systems, some Asus and Gigabyte models, etc.).

  4. Matt Cohen says:

    I hope you are still looking at this thread. I have a 790gx chipset motherboard. It supports RAID 5. I have 5 1tb HD’s. I want to run them all in a RAID 5. When I thry to initalize them in Windows Vista I get errors. I can only make it work at 2048 Gig. I should get 4tb of usable space. Please help. Thanks


  5. Brent Trahan says:

    That 2048GB might be a limit of your mother board’s BIOS.

  6. Matt Cohen says:

    I think so too. Is there any other way to create one big raid 5. I was also thinking of creating a raid 5 and a raid 1. Would you put the OS one the 1 or the 5. I’m just trying to make my movies music and photos fault tolorent. I think its jacked that I’m limited to 2048. Thanks for any help!

  7. TooSharp says:

    You need to create two Raid 5 arrays that span all disks. One will be a smaller disk for your OS say 250GB or so and the other what ever is left.

  8. Dean says:

    Ok but here’s my problem. I have VISTA 64 bit on a laptop with one MBR hard drive and a DVD player/recorder. I also have a USB Hard Drive and a few USB Pen Drives. How can I convert my single internal hard drive (with the OS that I’m using) from MBR to GPT since Vista wont install on the external drive and the installation DVD doesn’t have the convert function (or am I missing something?) Is there some bootable media that will do this, or some other way?

  9. pin says:

    Dean, you can’t. You can only convert MBR to GPT if there are no volumes on the disk, there is no way to do this with a filesystem present.

    To do this you’d need another disk to shuffle the information onto first, delete the volumes and then convert to GPT, then shuffle it back. This becomes more complicated where you are talking about the boot volume, but that’s another question right there.

    Forgive me for asking, but why do you want GPT on your laptop anyhow? I’m going to assume you need more than 4 partitions?

  10. pin says:

    Matt Cohen,

    What version of vista do you have? If its only 32bit there’s your problem. I think the Sb750 southbridge supports 64bit LBA but since I’m not familiar with AMD kit I’ve no idea if you’d need to enable it someplace or not.. if it’s not enabled you’d have the 2TB limit…

  11. Alex says:

    I bought one 2.5″ Seagate HDD from eBay with Apple logo.
    It put it in enclosure and thought that I can use it as external
    drive for my PC that runs Windows XP. I was not able to access the drive though because it was GPT protected which I think was pre-partitioned for MAC systems. I Googled for the solution and here is the best one because it has step-by-step guides with photos.

    How to delete GPT Protective Partition?

    In Windows XP Professional, if you cannot access or modify GPT disk, you can convert a GPT disk to MBR by using the clean command in DiskPart, which removes all data and partition structures from the disk.

    1. You may see S2VR HD 5 Drives in GPT status.

    2. Go to DOS command line (click on “Start Menu”, then “Run”, typee in “cmd” in textbox, and hit “OK”)
    Type in “DiskPart” in command line.
    Type in “list disk” in command line to show all disks in this machine.
    Use “clean” command to remove GPT disks.
    After that, type in “exit” to end DiskPart. You can follow all commands marked as “RED” to delete all 5 drives in S2VR HD.

    3. Go back to Disk Management, you can see all S2VR HD disks are “unallocated” now. Right click on disk info, choose “Initialize Disk”.

    4. Choose drives you need in S2VR HD and initialize them.

    Source: http://www.caldigit.com/RemoveGPT.asp

    They have there detailed instruction with photos. It was of great help.

  12. CHOPPERGIRL says:

    Whenever I run diskpart, I get a G** D*** menu of partions, instead of a diskpart> prompt.

    Every FAQ I read on this (ie, http://support.microsoft.com/kb/300415) says if you run diskpart, you get this prompt from which you can do things like CONVERT GPT, but I don’t, I get a stupid menu.

    I’m running it off the Windows XP x64 setup CDROM, at the recovery console dos prompt, trying to create a GPT partion to install WinXP x64 on. You can’t do it from inside the blsted WinXP drive formatting menu.

  13. GenRabbit says:

    people, do not try to install WindowsXP64/Vista/2008 on your PC with GPT unless;
    1. its an Xeon based pc with EFI bios
    2. You are booting thru a hdd controller which can boot from GPT.

    Todays mainstream PC’s and motherboards can only boot from MBR, and that means your GPT can only disk’s for storage.

    • RedFlameOut says:

      Correct there.

      Windows Vista uses MBR for drives and that limits the size to 2 TB. To use GPT, which allows larger partitions, and to boot from it you must have an EFI based system. Some controllers support doing booting from GPT but from my experience it is not a good idea to boot from GPT if the mother/mainboard does not use EFI.

  14. Joe says:


    Do it by bootable OS media. You need only be more intelligent than the computer.

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