Windows 10: How to downgrade Windows 10 from 1709 to 1607

I think Windows Setup is ignoring your unallocated space because it's still too small. Try at least doubling it to 50GB, more if you can afford the space.

 

I've just done some research on MBR disks. See Windows Setup: Installing using the MBR or GPT partition style | Microsoft Docs.
It seems that my HD has been formatted as an MBR style since birth, and I installed Windows 7 then upgraded to Windows 10. I later got a new CPU and mobo, which supports UEFI.
What's curious to me is that Windows 10 still boots OK. Maybe the BIOS switches to legacy mode rather than UEFI to boot it.
Can I convert my HD from MBR to GPT without wiping it? Or could I just select legacy mode in the BIOS and would that allow my Windows 1607 DVD to install?

 

The installer says it cannot install into the space because it is MBR formatted. That is, when doing an install directly from the DVD.
I'll see if doing the install from inside Windows will let me at least choose one of the 4 partitions it does show, and if it allows me to proceed, then I'll try your suggestion. I'll post the result soon.

 

I have no experience doing this conversion on a live Windows system, but it appears to be possible according to one of Brink's tutorials. Don't try until you have a system image to restore in case it all goes horribly wrong.

Convert Windows 10 from Legacy BIOS to UEFI without Data Loss Windows 10 Tutorials

 

I expanded the unallocated space to 50 GB, but same result. You'll see that D: is now smaller than before.

 

50GB should be sufficient, post #17 may be your only option now.

 

I ran mbr2gpt from elevated command prompt:
PHP Code: C:\WINDOWS\system32>mbr2gpt /allowfullos /validate /disk:0
MBR2GPT: Attempting to validate disk 0
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
Cannot find OS partition(s) for disk 0

C:\WINDOWS\system32>mbr2gpt /allowfullos /validate /disk:1
MBR2GPT: Attempting to validate disk 1
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
Disk layout validation failed for disk 1

 

I don't think I have enough experience to help further. Read the subsequent posts in @Brink's tutorial thread, that error was one of the first questions asked in post #2, eventually solved.

Another poster asked about that in post #19, also resolved eventually.

 

If you downgrade to Windows 1607 and it works you are relying on a report in another thread.
If the downgrade to Windows 1607 does not work then you will have wasted time and at the same time learned new steps.
One of my computers has 1607 and support ends on April 10. There will be no more support for malware surprises such as Spectre, Malestrom, etc.
So there are pros and cons for 1607 > possible fix for the freezing but no guarantee and loss of Microsoft update support.
There are many threads reporting performance changes after BIOS upgrades and software upgrades for Spectre and Malestrom so if the link that fixed the freezing predates the January to March upgrades it creates some uncertainty about 1607 fixing the freezing problem.
Moving from MBR to UEFI should improve security and speed.
Consider trying Ubuntu to see if a non Windows operating system fixes the freezing.
If it fixes the problem then you can attribute the problem to the operating system.
If it fails to fix the problem then you can attribute the problems to hardware and then workup the hardware.

 

I've moved discussion about MBR2GPT to another thread. Help using MBR2GPT on my system - Windows 10 Forums. If you can help me, go there.

If you can figure out how I can install 1607 as a dual boot, with an MBR disk, I'd like to know how.

The only reason I want to run 1607 is to see if the freeze goes away. I don't plan to run my software under 1607 further, except without internet connection, to protect me from security threats or Windows deciding to upgrade to 1709.
I figure that if I can convert to GPT, then I'll be able to install my 1607 DVD from boot, or install it from the ISO file within Windows.

Problem with running ubuntu, or even linux under Windows, is that I'd have to write a new driver, at least to do repeated writes to the problem MSR and see if there's a freeze. That would be a whole new learning curve for me, longer than I want to spend.

 

At some point, my bcd store got hosed, and I had to recover from a recent system image.
That left me with System Reserved and D: on disk 0, and C: and Recovery on disk 1.
I added a partition H: taking space from D:. The disks are still MBR format.
I tried installing 1607 from my DVD. And miracle of miracles, this time it worked! Setup recognized H: and let me select it. I have no idea what went wrong earlier, but it doesn't matter. Here's the result.




I created H: by first shrinking D: by 25600 Mb, then doing a Make Simple Volume on the unallocated space. So this seems to be a recipe for success.

BTW, in the Windows 1607, I made my Ethernet connection a Metered connection, to prevent Windows Update from trying to upgrade me to 1709.

N.B.: I'd still like to convert my disks to GPT someday, and so my other post about doing this remains open and unsolved. I invite suggestions there.

Thanks to all who have contributed here!*Smile

 

Good, you now have a working 1607. To stop 1607 upgrading itself to 1709 but still allow you to get all the other updates you have to hide some updates.

Hide or Show Windows Updates in Windows 10

The first and most obvious one is the 'Feature update to Windows 10, version 1709'. You should also hide...

KB4091461 End of servicing notification for Windows 10 Versions 1507, 1511, and 1607
https://support.microsoft.com/help/4...07-1511-and-16

and...
KB4023814 Windows 10 display notification to install latest version
(that one installs the Update Assistant)

 

could try virtualbox don't lose any data or settings all you need is your iso win file to install on the virtual system easy to create..