How to establish Windows UEFI boot order on a machine with two Windows installs?

[ZippyDan]

So, I have a newish HP (Small Form Factor) "Business" machine.

It was previously running Windows 8.1 Pro on a spinner, but I have now upgraded it to Windows 10 Pro on an SSD drive.

When I installed Windows 10, I disconnected the other drive, because I've run into situations in the past where Windows will put the system partition on the old drive. I want to make sure that the new installation can run self-sufficiently entirely and exclusively from the new drive.

Now, when I plug the old drive back in (because I want to be able to access the files from the previous install), the system is always booting to the Windows 8.1 Pro drive.

So there are some obvious solutions here:

1. Unplug the old drive. Yes, then I can boot to Windows 10 just fine. But then I can't access my files on the old drive.
2. Put the old drive in a USB enclosure. OK. But I don't wanna!
3. Wipe out the old drive (after copying the files off). I will do that. But I want to figure out the cause of this problem!

There is another obvious solution, but it is not working and I want to know how to make it work

Change the boot order in the BIOS. Well, the SSD with Windows 10 is plugged into SATA0 and the spinner with Windows 8.1 is plugged into SATA1. I have specifically disabled SATA1 in the BIOS boot order, and moved SATA0 to the top, but that is only under "Legacy Boot Devices". "UEFI Boot Devices" is still at the top of the list, and under that is "Windows Boot Manager". I'm guessing that Windows Boot Manager is choosing the 8.1 Pro install for some reason.

(By the way, I know that SATA0 is functional in this configuration, because if I invoke the boot menu at startup, and manually choose SATA0, I can boot to Windows 10 just fine).

So my question is, how can I get the "Windows Boot Manager" to choose the Windows 10 SSD when there are two Windows installs available?

I tried running bcdedit in my Windows 10 install, but it only seems to be aware of itself (this may arise from the fact that I installed Windows 10 with the old drive disconnected). So am I right to assume that there are two Windows Boot Managers, one on each disk, each with no knowledge of the other?

In that case, what is making the BIOS choose the Windows 8 boot manager first, especially when it is installed on SATA1?

 

[VirtualLarry]

In that case, what is making the BIOS choose the Windows 8 boot manager first, especially when it is installed on SATA1?

Because that is the "Boot Manager" registered in the UEFI BIOS.

With UEFI, the OS installer "registers" the bootloader with the BIOS. It's no longer as simple as just listing the boot storage device order in the BIOS, and then reading the bootloader metadata off of the boot storage device.

 

[deustroop]

I found this from an FAQ, might help.

I have connected 3 hard drives to my new system. I would like to change the boot priorit of my hard drives, but I can only see one hard drive the boot priority menu. My question is, how do I cange the boot priority?
Please note that under the EZ Mode UEFI BIOS will only show one device of each type. To change the priority, please go into Advanced Mode, look for [Hard Driver BBS Properties] under [Boot] page, and change the boot priority from there.

Note: You may need to scroll down to the bottom of the [Boot] page to find [Hard Driver BBS Properties] item.

 

[deustroop]

I think that an eufi bios will only boot from an eufi aware disk.
The Asus bios (eufi) that I have will only boot drives with a "Windows Boot Manager" entry for the desired drive in the boot menu .
Expand the eufi devices list. You should have a manager for each .

 

[Ketchup]

So do you actually want a boot manager, or do you just want to be able to make the change from the BIOS?

I have read some good suggestions here for the latter, for the former, EasyBCD supports up to Wondows 10 and UEFI.

 

[JackMDS]

Second the https://neosmart.net/EasyBCD/ suggestion.

Free for personal use, easy to configure, and works very well.

 

[mv2devnull]

The UEFI has boot menu that can have multiple entries.
Each entry is stored in the motherboard.
For example:

# efibootmgr -v
BootCurrent: 0000
Timeout: 0 seconds
BootOrder: 0000,0001
Boot0000* CentOS  HD(1,800,64000,52..eb)File(\EFI\centos\shim.efi)
Boot0001  DTO UEFI USB Floppy/CD  Vendor(b6..8d,0500000001)AMBO

Two entries. The first (and default) shows label "CentOS" to the user
and loads file \EFI\centos\shim.efi from the EFI System Partition of a disk.

The shim.efi is a bootmanager. Bootmanager (even the MS one) can have multiple entries.
The entries can be on whatever partitions of whatever disks.

That gives two options:
1. Two entries in the UEFI, each loading a different bootmanager.
2. One bootmanager that has two entries, one for each OS.


You do have an additional hurdle: each of your installations is on "drive C:".
When you have both connected, which is C: according to the OS that you have booted?

 

[ZippyDan]

Ya, well I only have one Windows Boot Manager listed in the BIOS, even though 2 different installations of Windows have occurred on the system. I mean, how does the UEFI know to "unregister" a Windows Boot Manager instance if I were to remove a drive?

Also, as this is an HP computer, it comes with some HP BIOS which doesn't give a lot of options which I can change. :/

So it appears I have two Windows Boot Managers, one on each disk, but yet only one shows in the UEFI list. How does the UEFI choose which one to boot from?

The last question makes no sense... from either drive that I boot, that drive appears as the C: drive. I don't see how that is relevant, since drive letter are completely arbitrary to each installation and have nothing to do with BIOS/UEFI/booting.