XPost: alt.comp.os.windows-10

Hi Paul, Wildman, and Carlos,

(I will respond to Paul's advice separately, as this is already long.)

Thanks for your good advice:
 GRUB_DISABLE_OS_PROBER=true"
Which is what I needed and will take, as much as I understand it, as I
readily admit I never really understood how grub works (since it installs
itself in a dual-boot setup) and where you have explained to me already
more than I knew about my own Grub setup!

This is what Grub found this morning, booting with all 3 HDDs powered on:

o Ubuntu
o Advanced options for Ubuntu
o Memory test
o Windows 10 (on /dev/sda1)
o Windows 10 (on /dev/sda2)
o Windows 10 (on /dev/sda3)

I have never really understood this "sda" SCSI drive nomenclature since I
never use terms like "sda" except when I'm forced to, so I had assumed
(wrongly it turns out) that sda3 must contain the latest Windows 10, but
choosing sda3 failed to boot no matter what options I tried:
 
o Preparing Automatic Repair
o Diagnosing your PC
o Your PC did not start correctly

The same sequence happens with sda2, so sda2 and sda3 must be HDD1 and HDD2
(each of which has an "old" Windows 10), where HDD2 definitely also has the
older Ubuntu dual boot setup that I had never bothered to wipe out (but
where I don't know if that HDD2 is sda2 or sda3 yet since I never use sda
SCSI-drive nomenclature except in debugging situations).

The question is "where is grub coming from", given that HDD3 (which
previously had Windows 10 1803 + Ubuntu 18.04) was just "wiped out" a week
or so ago using a Windows 10 1809 ISO to perform a clean install on that
HDD3. [It seems clear that Grub must be coming from HDD2 since that's the
only possibility left!]

After the recent power interruption destroyed Windows 10 1803, I was able
to boot to Ubuntu 18.04, so it was only Windows that was affected by the
power outage.

Nonetheless, I wanted to start both new and clean, so I explicitly
disconnected HDD1 and HDD2 before I booted to a newly made Windows 10 1809
ISO and then I told that Windows 10 1809 boot GUI to destroy the previous
Ubuntu 18.04 partition along with the previous Windows partition (where the
plan is to install Ubuntu 18.10 as the dual boot companion to Windows 1809:
o 
o 

Given that, I had "thought" (and intended) that I wiped out Grub2 at the
same time, which I probably did ... but only on HDD3 was grub wiped out
(apparently).

Subsequent booting on HDD3 (with both HDD1 and HDD2 disconnected) showed no
hint of Grub, as HDD3 booted right to Windows (where I will add Ubuntu
18.10 soon).

Before I do that, I need to better figure the "boot sequence with grub"
out, since I had "thought" that connecting HDD3 explicitly on the
motherboard SATA1 port was how to tell the computer to boot to that
specific OS (which is the only working windows left).

But somehow, when I connect HDD2 and HDD1, the older Grub (from Ubuntu
17.04) is taking over, which is the sequence I need to try to understand,
since it's certainly an "older grub" that I don't want to be active.

I saw Carlos' suggestion of:
  ">You can easily create your own menu and disable os-prober."
Where I agree that the 'wrong' grub is running, which is then finding the
"wrong" Windows to attempt the booting process.

And I saw Wildman's suggestion of:
 "> Add this to /etc/default/grub"
 " > GRUB_DISABLE_OS_PROBER=true"
Where, in my plan, there should not be a grub in the first place (but
obviously grub exists, even as it's an "older" grub on a non-boot disk).

The interesting question is "where do I find this Grub", since, the HDD3
boot disk, which I specifically attached to the 1st motherboard port
(SATA1) doesn't have grub (as far as I know).

(Obviously, I will research more how to figure out why the 'wrong' grub is
taking over, and then how to stop that grub from activating itself.)

--- SoupGate-Win32 v1.05