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I have a notebook from my company that was installed Win 7 MBR + Legacy. I need to install a few programs, but they are not compatible with Win 7 anymore and I can't upgrade or do a clean install because there are programs that can't be reinstalled. I only have one hard disk, so I created an unallocated partition to install Windows 11 and make a dual boot.

But First, I converted my MBR disk to GBT. I used a program called Minitool partition to convert without losing any data and it worked. Then I changed the Boot Option on BIOS to UEFI(Without CSM). After that, I installed Win 11 without any problem, and everything is working great.

Now I have only a problem. When I turn the notebook on, if I select Win 7, I will be stuck on a black screen. So what am I missing here?

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    "I have a notebook from my company" => it is the company's problem ;)
    – Andrew Morton
    Jul 10, 2022 at 18:19
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    You converted MBR to GPT but did you make the required changes from within Windows to make it compatible with UEFI mode? Windows 7 had no automatic mechanic like Windows 10 did. WIndows 11 has MBR2GPT but it doesn't itself support Legacy Mode.
    – Ramhound
    Jul 10, 2022 at 18:37
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    I agree with @AndrewMorton. Your company hasn't provided you with the equipment you need to do your work. Even if you were to somehow make it all work, you are setting yourself up for future pain when your computer goes kaputz. You need to backup and virtualize any legacy environment to ensure that it continues to run when your hardware ceases to.
    – Stephen Quan
    Jul 11, 2022 at 6:32
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    If it's your company's computer, DO NOT INSTALL Windows 11!
    – Davidw
    Jul 12, 2022 at 0:19

2 Answers 2

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After a few hours of research, I found a solution! I'm going to describe what I did to help someone in the future.

  1. In BIOS, I changed the boot option to 'UEFI (WITH CSM)

  2. The "system reserved" drive from my windows 7 OS now shows up in my PC as the D drive, and my former C drive as the E. So, I removed the letter from the "system reserved". (You can do it through disk management)

  3. You need to run one command in a Command Prompt with Admin ("Run as Administrator") assuming that you have done nothing with changing drive letters, hiding partitions, etc.

    bcdboot **X**:\Windows /d /addlast (X - Put the letter according to the disk where Win 7 is installed)

  4. After that, it could boot into Windows 7, but it froze at 'Starting Windows'.

  5. I created a Win 7 installation media, then chose the option 'Repair this Computer', and after 'Startup Repair.

Now everything is working! I can switch between Win 7 and Win 11 without any problem.

Where I found the information: https://www.tenforums.com/general-support/4289-cannot-boot-into-windows-7-after-installing-windows-10-tech-preview.html

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Your Windows 7 version used BIOS+MBR and was a 32-bit version.

Windows 11 is 64-bit and is incompatible with MBR, so you converted the disk to UEFI+GPT. This rendered the Windows 7 version unbootable.

Your options are as I see :

  • Return to BIOS+MBR and remove the Windows 11 partition. Create and use instead a virtual machine with Windows 11.

  • Install a 64-bit version of Windows 7. This means that you'll lose your current installation.

Whatever you do, I suggest taking an image backup of the disk and ensure having a boot USB that can reinstall the backup. These manipulations of the disk are dangerous.

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