MBR2GPT Disk layout validation failed

macsrwe- I'm guessing you haven't found the "log" file and that's what's causing the confusion. So start there.

But, before I provide all these instructions, let me recommend you simply ignore everything about Win11 and stick with Win10. Why? Read the last portion of this reply and you'll know why.

Find and review the log: C:\Windows\setupact.log (NOTE: Use "Notepad" to view the file - right click and "Open with...", then select Notepad.

Once you locate and read the file, you'll probably be more confused. But it's not necessary to understand what "any" of that information already posted means. What you want to see is anything related to the validation. After you have run the MBR2GPT Validate and it failed, open the "setupact.log" file. The last line in the file should state why the validation failed.
For me, the last line was this: ValidateLayout: Last partition too close to the end of the disk. Should end at offset 1000204869120 or below, found at 1000204886016

So, that tells me the partition (if you can right click and see "Shrink" in the list that is not greyed out, you may shrink that partition) needs to be reduced in size.
Use a calculator and enter the larger number minus the smaller number. The answer to that calculation is the amount you want to "shrink" the "volume" (partition).

With that information you can open "Disk Management". If you are not sure how, use the "Search" field in the task bar on Win10 and search "Disk Management". The system will show "Create and format hard disk partitions", but if you click on that it opens "Disk Management".

Once you open Disk Management, in the lower section you'll see outlines of any drive you have in your computer. Single left click on the partition (just to highlight that partition) that you wish to shrink.

If the partition "can" be shrunk (and I can almost guarantee the one causing the problem "can" be shrunk), when you "right" click on the partition you will immediately see options. If "Shrink Volume" is an option (not greyed out), then click on that.

Another window opens and you see "Total size before shrink in MB:", "Size of available shrink space in MB:", "Enter the amount of space to shrink in MB:" and "Total size after shrink in MB:"
If you have done your calculation, "Enter the amount of space to shrink in MB:" is the only field you can change and that is where you want to enter the adjusted number in MB (megabytes). After you enter the amount to shrink, click "Shrink" at the bottom (it's like "Save").

The "difference" between the 2 numbers in the "setupact.log" is the number you want to input in the field "Enter the amount of space to shrink in MB:"

So enter the number you calculated (when you subtracted the smaller number from the larger number found in the log showing you the error) into that field. Then click "Shrink".

Follow the prompts and you are finished.

Now run the MBR2GPT Validation (using Command Prompt as administrator run this command: mbr2gpt /validate ) one more time. If you followed the instructions and entered the correct number into the only field you can make a change for shrinking, then you should find that you "Passed".

I can't think of any reason the above won't work for you since it's been used by so many who found they passed after the shrinking.

BUT!!!!! I'm going to say this and you should hear / listen. FORGET about the entire mess! Windows 11 is NOT ready for the general public! I don't care what you hear or read or even have information from Microsoft. If you have read or spoken to "experts" of the software, you'll hear them say you should just stick with Windows 10!
Even technical support told me (after I described I have 2 drives, one with Win 10 and one with Win 11) to just boot into Win 10. I had asked some technical questions and described what I just installed and the agent simply stated (more than once), just boot into Win 10. I didn't even ask why...I just said, "Understood."

You have to wonder, why is Microsoft already working on and has a rough delivery date of 2025 for Windows 12?

"I" can confirm that Win11 is not ready because no matter what's been done, the OS (operating system) video is NOT smooth. It's jerky. Most who do "some" on their computer may not notice. I spend an inordinate amount of time on my computer daily. I can see if something is not right. And I can easily notice how the screen is "jerky" - not smooth at all. I switch back to Win10 and everything is very smooth, working perfectly. It's not my hardware which is all new just 3 months ago. My video card is enough to easily edit videos. So it has the power and quality to run very smooth...but doesn't in Win11.

Additionally, I've run updates at least a dozen times in Win11 and each time there is a problem. Most often, updates freeze the Windows Update screen and there is nothing I can do but close the updater and reboot - "hoping" that will fix the issue. But it doesn't always. So if Win11 can't update properly, and the screen is jerky, WHY would I want to use Win11? It's just a problem waiting to happen.

I switch to Win11 about once a week just to update the drive. I spend a couple of hours on Win11, get frustrated with the jerky performance and boot back to Win10.

I'm telling you all of this so that others will also note, if you get your PC to be Win11 compliant, don't expect to have everything working perfectly like Win10.
And if you have not made changes to your PC for Win11, don't. Just keep using Win10. It will be updated through the time when Windows 12 will be released...which should also tell you something about Win11.