Help: Windows 10 / UEFI BIOS Dual-boot problem

Hi everyone,

My current system specs:
- AMD Ryzen 3.6GHz CPU
- AM4 motherboard with MSI Click 5 UEFI BIOS
- BIOS UEFI/CSM Mode: UEFI
- Secure Boot: Disabled
- M2 SATA SSD (call it SSD1)
- 2.5" internal SATA SSD (call it SSD2)
- Windows 10 Professional 64-bit (22H2), with Digital License linked to my Microsoft Account

I was a Windows 7 user on an old AMD system with legacy BIOS, but I'm relatively new to Windows 10 and UEFI system. I've been using Windows 10 on the above PC specs for about 2 years, without understanding how UEFI BIOS works.

A few months ago I bought an additional SATA SSD (SSD2), as I need to make the PC dual boot with the same Windows 10 OS. I do this because I need to have 2 separate system, where one system is used for some purposes, and another installation is used for another purposes, as if I had 2 separate PCs. It seems that I can use one Windows 10 Product Key for both installations on SSD1 and SSD2.

I forgot how I installed the 2nd Windows 10 OS to SSD2, but it worked.
From the UEFI Hard Disk Drive BBS Priorities menu, I had been able to switch the active booter OS between SSD1 and SSD2, without issues.

In the latest months, I'd been using Windows 10 on SSD1, until a few weeks ago somehow I noticed that I couldn't boot into SSD2 from the UEFI BIOS anymore. I tried to Repair the OS from the Windows 10 Installer USB, but it's not repairable. I noticed there was only 1 boot option in the UEFI Hard Drive BBS Priorities menu; the other boot option was missing. I remember there was some electricity blackout a few months ago, plus a UPS battery failure, so the PC was shut down abruptly.

I could still boot into Windows 10 on SSD1 that time.
SSD1 is Disk3 in Windows Disk Manager (please see the attached picture).



So I reinstalled Windows 10 on SSD2 and all the additional software.
SSD2 is Disk2 in Windows Disk Manager.

After that, I had been using the OS on SSD2 for weeks.
But when I tried to switch to SSD1 from the UEFI BIOS, it happened again. This time, SSD1 was missing from the UEFI Hard Drive BBS Priorities menu, so only SSD2 was bootable.

So I reinstalled Windows 10 into SSD1. This time, I unplugged the SSD2 power cable to make it undetectable on UEFI BIOS, hoping my SSD1 OS installation wouldn't damage the one on SSD2.

But to my surprise, after SSD1 OS installation is finished, and plugging the SSD2 back, it happens again, now SSD2 is not bootable anymore. After unplugging CMOS battery and putting it back, and updating MSI UEFI BIOS with a newer version, trying to Repair the OS from Win10 Installer still won't work. I also tried using EasyUEFI Trial, but it doesn't work either.

So I'm confused what to do now, in order to repair (if possible), or to properly reinstall Windows 10 onto SSD2.
To make it clear, my goal is to have 2 Windows 10 installations (SSD1 and SSD2) that is switchable in the UEFI Hard Drive BBS Priorities menu.

Would anyone please give me the step-by-step procedure to do this?
Thank you in advance for your help.

Megahertz said:

What is happening here is that you are installing Win 10 without removing the other Win 10 SSD. Then, during the installation, it finds a boot manager on a EFI Fat32 partition on another drive and put the boot manager of the new installation there. You can only boot with the drive that has the EFI partition (drive 3) attached. At the moment they aren't independent installations.

You can create a EFI partition on drive 2 and load it with the boot manager but the best solution is to remove the other M.2 SSD on drive 3 and do a clean install on drive 2.
In other words, I recommend a Clean install detaching all other drives.

Thank you @Megahertz for the explanation.
If I understand it correctly, my mistake was when I reinstalled Win10 to SSD2 without unplugging SSD1 first.
Please correct me if I'm wrong; Therefore, to fix it, now I just need to clean install Win10 to SSD2, by unplugging SSD1 first.

Did you try to launch the Boot Menu during POST (F12)? You should see two options, one for each installation.

I didn't try it; I just directly entered the UEFI BIOS (by Del button), and accessed the Boot Options menu in there.

Do you have any other drives on disk 0 and 1?

Yes, Disk 0 and 1 are SATA HDDs that contain only Data, in NTFS format (no OS or Programs). Please let me know if I need to unplug them too when clean installing Win10 to SSD2 later.

Thanks again Megahertz for your help, really appreciate it.

Got it, thanks again Megahertz for the clear explanation, really appreciate your help.

Thanks so much @Megahertz, it works!

Both SSDs are detected in the Boot Menu now:


There was a little issue; When I booted into SSD1 and ran Windows Disk Manager (diskmgmt.msc), it detected Win10 System and Program partitions on SSD2, saying they had Errors. And the strange thing, it displayed the old partitions (the previous drive C and D before the clean install). The same thing was reported by Macrorit Partition Editor too, but Minitool Partition Wizard didn't. And after rebooting, Windows 10 said there's error in the said volumes, and it ran some automatic disk repair.

After that repair, it's running well until now.
I tested it again, by switching booting from both SSD1 and SSD2, and it seems the error has gone. Hopefully there's no other unexpected things happening with this PC.

Thanks again Megahertz, I think the original Dual-Boot issue has been solved.