Conversion of Legacy to UEFI Win 10

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  1. Posts : 13
    Win 10 Home 64bit
       #1

    Conversion of Legacy to UEFI Win 10


    Hi, This is a newbies first post. I need to set up this system, Win 10 64bit 21H2 build 19044, 1766 to comply with Win 11 requirements by using TPM and secure boot. The mobo is B450M Mortar MAX which has TPM available, ie no external module required.
    But first I need to change from Legacy to UEFI using your tutorials and I see your comment "You will only be able to convert a 64-bit Windows 10 to UEFI on a computer with UEFI firmware (BIOS) enabled." This seems to be a catch 22 since the system will not boot with UEFI enabled in BIOS since the HDs are in legacy mode. Do you mean once the conversion has been made, then UEFI must be enabled in BIOS ?
    Secondly, I have been using Macrium Reflect to create images. After conversion, will these images be incompatible?
    Many thanks for all your tutorials, well written.
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  2. Posts : 43,460
    Win 10 Pro (22H2) (2nd PC is 22H2)
       #2

    Welcome to tenforums. Presumably this is the tutorial from which you are quoting?

    Convert Windows 10 from Legacy BIOS to UEFI without Data Loss

    I've asked the question for you at the end- may be worth clarifying in the tutorial - now done. (Thanks Brink!)

    If you read Option 1 the sequence seems clear.

    Related:
    Convert MBR Disk to GPT Disk in Windows 10

    Great that you are using disk imaging- naturally you will ensure you have a current disk image stored separately and securely before attempting this.

    Once you have completed the conversion successfully you will need to start a complete new disk imaging sequence starting with a new full disk image (of all 4 UEFI partitions).

    FWIW you would still be able to mount and access your old images, but that would be of little value.
    Last edited by dalchina; 15 Jul 2023 at 08:53.
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  3. Posts : 13
    Win 10 Home 64bit
    Thread Starter
       #3

    Legacy to UEFI


    Thanks dalchina, all clear and glad the anomaly was corrected ! I will make images before conversion and after as you suggest. I had help in trying to resolve the problem, (that of enabling TPM and Secure Boot) but it was put down to an old BIOS version. In fact the issue, (legacy/uefi) was more fundamental and consequently was overlooked. I appreciate your very quick reply and as a first time user of TenForums, I am very impressed.
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  4. Posts : 13
    Win 10 Home 64bit
    Thread Starter
       #4

    Complications UEFI conversion


    Apologies for this lengthy post. Since my recent post regarding changing to a UEFI system, I elected to validate my system for conversion to UEFI using mbr2gpt.exe /validate. Since I was doing this through the running Win 10 system, I also had to use the / forallos option. As expected, because two SSDs had four partitions, the validation failed. A disc map is attached showing the current situation. Sorry, not uploaded since it is invalid doc file. Will sort this later if required.
    Which is where things fell apart. On the next boot, the system booted from the SSD (Win OLD) which in fact contained an old version of Win 10. I was totally unaware of this since the system had been booting off another SSD (Win 10 NEW) for months. (The reason for this was that I decided some considerable time ago, to clone Win 10 onto the larger SSD Win 10 NEW, but left the Win 10 OLD SSD connected and altered the boot priority to boot off Win 10 NEW. This was not a dual boot situation and I left the Win 10 OLD in place as a fall back option)
    Days after the validate, things became suspicious when Windows Update reported that my device was missing important security updates and so began downloading all the updates which the non operating Win 10 OLD had missed. I finally tumbled to what was going on when I saw that Win 10 OLD was now the C: drive. Now, OLD has downloaded all 21H2 updates and has commenced downloading 22H2. The reason for this is that support for 21H2 has ceased and Windows Update automatically downloads 22H2.
    So it appears to me that the validate had recognised Win 10 OLD, it was on Disk 0, and proceeded to accept the MBR but rejected validation based on the four partitions. Not sure about this since the three recovery partitions are empty. Attached is the disc map.. At the same time, it seems to have disabled the MBR on Win 10 NEW. Consequently, I now cannot change the boot priority since the BIOS no longer recognises Win 10 NEW as it is now a non bootable drive. I had not expected the validate to alter MBR on Win 10 NEW.
    I think I have some options.
    1) Change nothing and let OLD update to 22H2. Then decide :
    a) To use an image I made of Win 10 NEW prior to requesting the 22H2 download to restore NEW ie complete with its own MBR. I can then change the boot priority to boot off NEW.
    Or
    b) Image the newly updated OLD, (22H2) and clone that onto the larger SSD. I can then choose NEW in BIOS to boot from.
    2) It may be possible to rewrite the MBR in Win 10 NEW so that it can be seen as a bootable drive in BIOS.

    I do not understand why the validate operation removed the MBR from Win 10 NEW.
    I do not understand why Avast security would not have had to download all the updates necessary to Win 10 OLD although it did flag that I was not protected. Checking on my Avast account showed that all was well as did Windows Security. Eventually after a couple of days the flag disappeared which suggests that Avast had brought itself up to date although it is set to update manually.
    Hope I haven't bored you all with this but it has been a struggle to decipher what was happening. If I have it wrong, perhaps someone could advise. I don't normally like to quote my age but perhaps at 87, I am getting a bit beyond all this !

    - - - Updated - - -

    This is the disc map which I had to convert sorry for delay
    Attached Thumbnails Attached Thumbnails Conversion of Legacy to UEFI Win 10-disc-map-win-10-20-7-23.jpg  
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  5. Posts : 43,460
    Win 10 Pro (22H2) (2nd PC is 22H2)
       #5

    Hi, as you've discovered it's really not a good idea to have two separate Win 10 installations on separate disks in place at the same time. I suggest you choose one installation and have only that one in your PC.

    As regards the Recovery partitions, you can see what you get when you run this command from an admin command prompt:
    Conversion of Legacy to UEFI Win 10-1.jpg

    Post a screenshot of the result - but as you say, they are empty.

    @Bree - Hi, wondered if you can help here? I've only ever used UEFI installations so have never needed to do a MBR-GPT conversion. Thanks.
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  6. Posts : 3,543
    Windows 10 Pro 64-bit 21H1 (May 2021 build 19043.1083)
       #6

    I have done the opposite, that is to convert a GPT installation to MBR by deleting the extra needless partitions, expanding Windows partition to take all unallocated disk space and then use the Windows Setup USB to repair startup.

    I think the procedure to convert MBR to GPT should be similar. Shrink the Windows partition (if required) to create the required unallocated space and then create the small FAT32 system partitions. Convert MRB to GPT and then use the Windows Setup USB to repair startup and make the system bootable again. Of course you should use a GPT UEFI USB flash drive. If your USB is MBR, use Rufus to create it again in GPT UEFI format from the Windows 10 ISO.

    However, I don't think you need to go through all this trouble just to upgrade Windows 10 to 11. Just bypass compatibility check and the Setup should let you upgrade your current MBR system to 11. You can find all the details here: Let's install Windows 11 on incompatible hardware | Windows 11 Forum In short you have to create a new text file and rename it to appraiserres.dll (without the .txt extension at the end, so you must have enabled to show extensions). You download the Windows 11 ISO, mount it (Open with Explorer), disconnect from the Internet (to avoid a hidden online compatibility check) and run Setup. Before proceeding, go to the hidden folder C:\$Windows.~BT\sources, delete the original appraiserres.dll file and copy-paste the dummy you created with the same filename. Now you can proceed, Setup will be unable to check for compatibility and will go to the next stage. The upgrade from now on should be the same as upgrading from one version of Windows 10 to the other. Once the upgrade has completed successfully and you are at your desktop you can safely reconnect to the internet. You can run Windows Update and install all updates. To upgrade to 23H2 in October, simply download the new ISO and repeat the procedure.
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  7. Posts : 18,454
    Windows 11 Pro
       #7

    It is a very easy fix, but probably will have to wait for 10 hours until I get home tonight from work.

    The command to make D: bootable is:
    Code:
    bcdboot D:\Windows /s D: /f BIOS
    Then run
    Code:
    reagentc /disable
    Delete all of the recovery partitions.
    The you can use mbr2gpt.

    There, solution so simple I posted it from my phone!
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  8. Posts : 32,276
    10 Home x64 (22H2) (10 Pro on 2nd pc)
       #8

    datcoor said:
    ...first I need to change from Legacy to UEFI....
    Secondly, I have been using Macrium Reflect to create images. After conversion, will these images be incompatible?
    dalchina said:
    @Bree - Hi, wondered if you can help here? I've only ever used UEFI installations so have never needed to do a MBR-GPT conversion. Thanks.
    I have needed to convert from Legacy/MBR to UEFI/GPT just the once. My System One below was for many years my main machine, but I wanted to migrate it's Windows 10, all its installed software, and my user data to a newer UEFI machine that would be Windows 11 compatible. Like datcoor, I too use Macrium Reflect to image all my machines.

    I first clean installed the same version of W10 (21H1 at that time) on the new machine as a UEFI install in order to create all the correct partitions needed for UEFI. Then I restored just the C: Windows partition from the image of the old Legacy/MBR machine as a replacement for the newly created C: partition. It doesn't matter if the two C: partitions are different sizes, Reflect can adjust the size of the partition to fit as it restores it. I then ran the Reflect recovery USB's 'Fix Windows boot problems' tool to create the correct BCD entry.

    In addition, my old machine and the new one had quite different hardware. As the OP is converting MBR to UEFI/GPT on the same machine that won't be an issue for them. On the first boot Windows had to set up a lot of new drivers. The new machine is AMD based, whereas the old machine was an Intel system. When done, it booted to the desktop with everything present and functioning just as it had been on the old machine.
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  9. Posts : 6,669
    Windows 11 Pro - Windows 7 HP - Lubuntu
       #9

    I have used MBR2GPT many times, even on Win 7.
    Detach all other drives, boot from the drive you want to convert, open a CMD window as administrator and type:
    reagentc /disable

    Then delete the recovery partitions of the drive you booted from.
    Once all recovery partitions has been deleted, expand the C: partition to the end of the drive.
    I suggest you boot from a Win 10 or Win 11 installation drive, open a CMD window and type:
    mbr2gpr /validate
    If OK type:
    mbr2gpr

    It will convert the main drive from Legacy - MBR to EFI-GPT
    Then change BIOS and boot.
    Repeat the process on the other drive.

    Answering your question, yes you can use an old drive image made from a Legacy MBR on the UEFI GPT drive.
    You don't recover the whole drive image. You delete the C: partition and recover only the C: partition from the image, and keep the EFI and MSR partition.

    Another solution to convert the drive from Legacy - MBR to EFI-GPT
    You can also convert the drive from MBR to GPT using Mini Tool Partition and then create the EFI partition and MSR using diskpart
    Last edited by Megahertz; 20 Jul 2023 at 18:32.
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  10. Posts : 13
    Win 10 Home 64bit
    Thread Starter
       #10

    Thanks to all


    To say I am impressed with all the replies to my issues is an understatement. To dalchina, Megahertz, Bree, NavyLCDR and spapakons, all valuable suggestions. So give me a while to digest and I will come up with a plan. It looks like there is a way out of this, just want to be sure I take the right one. Thanks again to all.

    - - - Updated - - -

    Plan for TenForums
    1) Run reagentc and post. Note Windows RE status: Disabled Done
    2) Allow Win 10 OLD to update to 22H2 for use as standby if all
    else goes wrong.
    3) Use NavyLDR suggestion to make Win 10 NEW bootable (D:) and post Done but no success
    4) Boot NEW and update to 22H2.
    5) Review Bree and Megahertz suggestions and do the conversion to UEFI on NEW. When all set up disconnect OLD drive.
    Comment
    Prior to all this, I ran scannow on NEW. There were some problems but even an online repair was unable to fix them. Also ran scannow on OLD which has no problems. This is possibly since OLD has been updated with all Windows updates from an early version so is effectively clean. NEW has been operating with updates as they happen so possibly some corruption has occurred. But very strange that online repair will not correct this. So there is an option here to incorporate Bree's suggestion. But sort this out when 1) to 5) have happened
    Again many thanks for all the comments..

    - - - Updated - - -

    NavyLCDR said:
    It is a very easy fix, but probably will have to wait for 10 hours until I get home tonight from work.

    The command to make D: bootable is:
    Code:
    bcdboot D:\Windows /s D: /f BIOS
    Then run
    Code:
    reagentc /disable
    Delete all of the recovery partitions.
    The you can use mbr2gpt.

    There, solution so simple I posted it from my phone!
    My apologies . I should have elaborated. After running these commands, D was not shown in BIOS as a bootable drive. Also the disc map remained the same. Presuming that this had something to do with the fact that reagentc was disabled, I tried to enable it and then run the Boot D command again. But the result is shown in the attached. I hesitate to delve deeper into reagentc without knowing the detail
    Attached Thumbnails Attached Thumbnails Conversion of Legacy to UEFI Win 10-create-bootable-d-21-7-23.jpg   Conversion of Legacy to UEFI Win 10-reagentc-run-21-7-23.jpg   Conversion of Legacy to UEFI Win 10-reagentc-enable-22-7-23.jpg  
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