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?
After a few hours of research, I found a solution! I'm going to describe what I did to help someone in the future.
In BIOS, I changed the boot option to 'UEFI (WITH CSM)
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)
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)
After that, it could boot into Windows 7, but it froze at 'Starting Windows'.
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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