Unable to boot or install Windows after new Motherboard.

[Daymin]

In the process of rebuilding my PC I changed motherboards but kept all other components but now my existing Windows install is not found and I'm unable to install Windows with the Windows Media Creation Tool.

I assumed that only changing the motherboard I can simply connect my drives and resume where I left off but the OS does not get detected.

 

Here is my setup and my troubleshooting steps so far:
Gigabyte X570 I Aorus Pro Wifi (BIOS Version F11)

Ryzen 1700X (1000-Ryzen isn't officially supported on X570 but works with some BIOS versions)

Corsair 2x16GB RAM

Samsung 970 EVO Plus NVME

 

BIOS settings are reset to default ("Load Optimized Defaults" whatever that means)

Boot drive passes Device Self Test in BIOS
All hardware gets detected in BIOS
CSM Support is Enabled

• LAN PXE Boot Option ROM: Disabled
• Storage Boot Option Control: UEFI Only
• Other PCI Device ROM Priority: Legacy Only

If I try to boot into my boot drive I get the "An operating system wasn’t found. Try disconnecting any drives that don’t contain an operating system. Press Ctrl+Alt+Del to restart" message.
If I boot into "UEFI: STORAGE DEVICE 1532, Partition 1" (Windows Creation Tool) I'm unable to install Windows as the boot drive is MBR and not GPT.
If I boot into "STORAGE DEVICE 1532" I can start the Windows installation but during the restart which the setup does it does not continue the installation and just goes back to the start of the setup.
In the Advanced Options menu in the pre-install environment, I can now choose to continue to Windows 10 but if done so the PC restarts, and I get the no OS message.

I went into CMD from the WindowsPE environment and on my boot drive D: there is now a Windows, Windows.old, and Windows.old.000, because of two failed installation attempts.
I have deleted the Windows.old.000 folder as it was empty but my original install with all my files is now in Windows.Old.

I  moved the folders from Windows.Old into D: again while moving the corresponding existing folders in a "WinOS"-Folder.
CMD inputs I used for this process.
 

Spoiler

D:
md WinOS
move Windows WinOS
move "Program Files" WinOS
move "Program Files (x86)" WinOS
attrib –h –s –r ProgramData
move ProgramData WinOS
move Users WinOS

move Windows.old\Windows
move "Windows.old\Program Files"
move "Windows.old\Program Files (x86)"
attrib –h –s –r Windows.old\ProgramData
move Windows.old\ProgramData
move Windows.old\Users

 

I know a clean reinstall on a formatted drive is the best approach but losing the data on my boot drive is not an option and I do not have another system from which I can backup the data from the NVME drive.

 

How can I boot into my existing Windows installation or reinstall Windows without losing the existing data on the boot drive?

 

 

[DontBeSillyWrapYourWilly]

59 minutes ago, Daymin said:

I assumed that only changing the motherboard I can simply connect my drives

Well you've assumed wrong , lol. MOBO/CPU swap is pretty much always = windows reinstall. Even if it would boot system stability would probably be awful due to wrong chipset drivers and so on.

 

Put that drive in some other PC as just storage drive, take out what you need , reinstall windows.

 

 

[Alan G]

1 hour ago, Daymin said:

I  moved the folders from Windows.Old into D: again while moving the corresponding existing folders in a "WinOS"-Folder.

Do you have a second drive in this system??  Boot drive is always C:   If you do not have access to a 2nd computer, the simplest solution (it is cumbersome as it involves several steps but you will get all your data back) to your problem is to get a cheap SSD, remove the NVME drive, do a clean windows install with the SSD.  Add the NVME drive back in, make sure the computer boots with the SSD.  Now you can transfer files to the new SSD drive.  You can then put the NVME drive back in, format it; disconnect the SSD and install windows.  Going forward, it's always best to have a separate drive that is used just for data storage!

[Daymin]

Figured out how to fix it myself without having to reinstall or make a backup:

 

With the Windows Media Creation Tool on a USB-Stick access the Command Prompt in WinPE:

• Troubleshoot” > “Advanced options” > “Command Prompt”

And then input the following list of commands:

1. “bcdboot D:\Windows /S D:" (replace D: with the drive volume your Windows is installed on)
2. diskpart
3. list disk
4. select disk 0 (replace 0 with your boot drive
5. list volume
6. select volume 1 (replace 1 with the drive volume your Windows is installed on)
7. active

After those inputs and a restart, I could boot into my original install without problems.

 

Here is a tutorial for MBR and GPT drives.

In my case, I had to change the drive letter designation of a secondary drive for all my folders and programs to work.