Dual boot lost after new motherboard install.

[mittewi]

Yes - I know you're going to tell me I should reinstall Windows; I know that's my last resort, but I've been through this rodeo before and I know it can be done. Spending the next week and a half reinstalling software and utilities just does not sound like fun!

So - I had a dual boot from two separate HDDs with Windows 7 & 10. Just rebuild the PC from a Phenom 9950 on a GA-MA78GPM-UD2H motherboard, to a Ryzen 5 1600x on a Gigabyte GA-AB350 gaming 3 Motherboard. ('bout damn time!)

I arranged my disks so the boot order was DVD-ROM, Windows 10 HDD, Windows 7 HDD. When I booted, it went down to the Windows 7 HDD. Chkdsk ran and I was able to get into Windows 7 fine. I haven't loaded the new Motherboard drivers yet, so only the old ps/2 keyboard works, but that was enough to satisfy me for now.

This happened several times with the Windows10 Insider Builds/Technical Previews so I got used to having to reestablish the dual boot, but that was well over a year ago now.

So I disconnected the windows 7 drive to start investigating the Windows 10 installation. Here's what I've tried:

■ Changed the BIOS settings for UEFI and Windows 10 features, but still no boot.

■ Boot from Windows 10 Retail USB. to try Startup repair, but it fails.

■ In the command prompt, trying to run bootrec /fixmbr and /rebuildbcd commands but they give me an I/O error. But, bootrec /scanos does show a Windows Installation and Diskpart does show the drive, so I know it's connected.

If someone has a solid grasp on this boards UEFI/ Windows 10 features, Id' love a better explanation; perhaps my problem lies there.

I'm also considering moving the HDD back to the old motherboard to problem solve, but I'm wondering if there's something else I should try first. Suggestions?

TLR - I want to recover an old Windows10 installation when attached to a new motherboard.

 

[Colif]

i think using bootrec with both hdd attached is best way to achieve what you want to do. You need to add the GUID of the Win 10 drive into the windows boot manager in the bios, and I think a combo of bcdedit & bootrec is best approach

See if this helps: https://www.lifewire.com/how-to-rebuild-the-bcd-in-windows-2624508

 

[mittewi]

I figured it out and am posting the solution here for future searchers. I found a thread on another site that talked specifically about using bootrec from the command prompt on Windows recovery from a flash drive.

When running command prompt from the Windows Flash Drive, one of two things can get in the way:
1) the flash drive and disk drive are not formatted the same (UEFI or legacy) or
2) while the BIOS may support the USB3 drive, the Windows PE environment may not support it leading to errors.
I didn't figure out which of the two issues I was specifically up against, but either seem to cause the errors "the requested system device cannot be found" or "the request cannot be performed because of an I/O error"

All I did was stopped using the flash drive and pulled out the DVD I'd burned of the original Windows 10 Pro 64 bit RTM.
Using the DVD's Windows PE command prompt I used Diskpart /list volume.
Then I marked my Windows 10 volume as "Active" and exited Diskpart.
I was then able to select C:> and run Bootrec /fixmbr and /rebuildbcd.
That was enough to get the PC to recognize the Windows 10 installation!

Because of the New motherboard, it still booted to Windows PE, and "made repairs" before letting me into Windows 10 - but I got in!


TL-DR - after two nights of troubleshooting the issue was solved by simply using a Windows DVD instead of the retail Windows flash drive!