Solved Installed Windows 11 on a separate partition, Windows 10 now inaccessible

I recently upgraded to Windows 11 while upgrading my self-built PC's hardware. It turned into almost a complete gut job except for the hard drives. I added an M.2 SSD and planned to install Windows 11 on that and dual boot my Windows 10 setup for a softer transition. Unfortunately, while Windows 11 works just fine, my dual boot ideal has failed and I no longer have access to my Windows 10 setup. The hard drives are all good, they are there and files are accessible, but I cannot boot into Windows 10. I honestly don't care about keeping Windows 10, but I wanted to have access to all of my programs and gradually build them up on the other partition.

From my research I've learned that UEFI / GPT are very different from BIOS / MBR. I still don't know much about that other than they don't play nice. On the advice of one article I used AOMEI Partition Assistant to convert my Windows 10 drive from MBR to GPT. That was successful in it's conversion, but failed to make it a dual boot option.

My question for you all is: 1) Is there a way to turn this around and make it a working dual boot situation, or am I too far down the rabbit hole to go back, and 2) Since I don't really care about Windows 10, is there a way to access the programs I have installed on my Windows 10 partition from Windows 11, since all the data is there.

Much appreciated,
-Jake

type on Windows 11

bcdboot E:\windows (where, E: is Win10 OS partition)

done for your dual-boot.

I attempted that and something appears to try to happen, but nothing actually does. It looks like a window outline appearing and immediately shrinking off-screen (gray outline of a window that instantly flies and fades down to the bottom left corner of the screen).

1) Please run disk partition info > post a share link






2) Open disk management > post a share link

Use EasyBCD utility to add Windows 10 to BCD.

Hi.

If Windows 10 is on MBR-partitioned disk and Windows 11 is on GPT-partitioned disk, you can still access Windows 10 and boot to it provided that CSM is enabled in BIOS. I have used Windows this way for years. But you can only boot to Windows 10 through BIOS by choosing the disk drive on which Windows 10 is installed as first boot device. If you make this disk drive permanent as first-boot drive, Windows 10 always boots. You can choose any drive as first-boot drive.

Hope this helps.

suatcini54 said:

Hi.

provided that CSM is enabled in BIOS

Click to expand...

Was the Windows 11 a supported or an unsupported installation using UEFI with CSM?

zbook said:

1) Please run disk partition info > post a share link

https://www.tenforums.com/attachments/bsod-crashes-debugging/355861d1640707960-batch-files-use-bsod-debugging-diskparinfo.bat

Batch files for use in BSOD debugging - Windows 10 Help Forums

Information This thread is for use by the BSOD team to store batch files that can be used to collect additional data, fix settings or anything else that is useful in debugging BSOD problems in Windows 10. The way I see it working is the first

www.tenforums.com

Batch files for use in BSOD debugging - Windows 10 Help Forums

Information This thread is for use by the BSOD team to store batch files that can be used to collect additional data, fix settings or anything else that is useful in debugging BSOD problems in Windows 10. The way I see it working is the first

www.tenforums.com

2) Open disk management > post a share link

How to Post a Screenshot of Disk Management

How to Post a Screenshot of Disk Management at Ten Forums

www.tenforums.com

Click to expand...

Hopefully I've attached the requested info properly. Let me know if not.

Hi.

You have both Windows Oses on GPT-partitioned disk drives.

Can you run BCDEDIT /ENUM /V command in a command prompt window run as administrator and post a screenshot ?

My dual-boot system is given below after running the command:


Compare yours with mine. You should have two Windows Boot Loader sections for your system like mine.

Hope this helps.

@_Ed_
According to your diskpart info all you drives are GPT.



The command

bcdboot F:\Windows

Should give you a dual boot menu.

I have three questions to ask. 1. are they on the same drive? 2. If separate drives did you disconnect the drive with Win 10 before installing Win 11. 3. Did you turn off Fast Start in Win 11 and Win 10? Not talking about the Fast Boot option in the BIOS.

Scott said:

@_Ed_
According to your diskpart info all you drives are GPT.

View attachment 125772

The command

bcdboot F:\Windows

Should give you a dual boot menu.

Click to expand...

Sweet! I think this resolved it. On reboot Windows 10 did show up as a selection, and seemed to boot up just fine. I'll boot back into 10 after I finish this message to try things out and make sure it's all working fine, but I do believe this issue is solved. Thank you.

_Ed_ said:

Sweet! I think this resolved it. On reboot Windows 10 did show up as a selection, and seemed to boot up just fine. I'll boot back into 10 after I finish this message to try things out and make sure it's all working fine, but I do believe this issue is solved. Thank you.

Click to expand...