Changing hard drive order and number and Windows won't boot anymore

So I am just wondering what best practices are here. Please no nonsense answers and telling me I am doing everything wrong, whatever I do, okay.

Previous experience indicated that Windows 10 was capable of switching between IDE and RAID and AHCI settings without much problem.

I have a Windows 10 installation that I installed on some Gigabyte 780G motherboard.

I think I installed it with only one disk present and then later ran it as the 2nd disk and it worked.

I probably ran it in AHCI mode mostly.

Then later I replaced the motherboard with some Asus M2N motherboard and I got issues.

Predominantly the system failed to boot if it wasn't the 2nd disk, so I got boot failures until I connected back the first disk (that is unused by Windows) as I recall it. Other than that, it worked, and probably in AHCI again.

Now I have replaced the motherboard with some Abit AX78 mobo. It uses an older chipset (760) and is also slightly older. It is connected as the only disk and it boots just fine. I find that it has "Native IDE" set as mode, and Windows is just painfully slow harddisk wise.

This mobo is annoying because it doesn't have a boot menu (WHAT?) ... yes, (WHAT?!!!). So in order to boot from USB stick that has a copy of the Grub loader installed for this system, so I can boot Linux (that is on the disk too) I have to select the freaking USB stick as first boot device. Great. Anyway, it *might* be functional in the end.

However when I do so, and Grub loads, and I select Windows from the list, Windows activates but it instantly reboots. Upon next attempt it loads some Automatic Repair which never does anything useful that I've ever seen, no matter how many times it runs. It keeps rebooting. At first I think it must be some AHCI setting that I've changed, but it remains the same with Native IDE. Tough luck, this doesn't work.

Removing the USB stick from the boot order again (but not from the computer) Windows will only boot in IDE mode. In AHCI mode it says it cannot find my boot device. Bummer.

Now what? This system ran fine on another AHCI-enabled system. Actually that was the first mobo I mentioned. And probably another one before that. Currently this system will only boot if it is the first boot device AND it is set to IDE mode.

Yeah, great.

I mean, what the hell can I do about this?

Moreoever, I'm okay with installing Windows again or restoring from a backup. But then what?

If I install it with the other (real) disk present, it might not boot if that real disk is absent. Windows should not use that disk, but it might still depend on it in its fancy imagination of the moment.

This whole system becomes pretty unworkable if every hard drive addition ever is going to make the system not boot anymore. This just plain sucks.

And not in a good way, I might add.

And what if I want to move it to some RAID controller? What if I turn RAID on? It used to boot fine when put to some cheap Delock raid controller as long as I made a RAID array out of it (JBOD was fine). I can check what happens of course: I also have a Highpoint controller in this system now that goes unused, so I can check what happens if I put it on there in JBOD mode. Then it will be first disk, but I don't know what Windows is going to do because eventually the RAID (if I do this) is not going to be the prime boot device, so Windows will still be on the second disk. (I will have to make "Addon-card" the first device to even boot from it, I think.

I notoriously want to BOOT from a disk windows is NOT installed on so that I can keep the Windows boot loader on the disk that Windows IS installed on so that the whole disk works without the other disks and that was the whole PURPOSE and yes I am angry about this. How is this so hard to ensure a system that will just work?

Microsoft, Jesus Christ Microsoft, what have you done this time? This just stinks.

Linux will boot from anywhere, as long as you give the required parameters at the start, it will run. Windows is incapable of detecting the "boot partition" (2nd partition) on a disk it has already freaking loaded the "system partition" from!!!!

What the????

On the original motherboard, this thing worked. I think on the 2nd motherboard it also started working after I got it running the first time, I don't know.

Now it won't even run in AHCI mode even though the freaking system was installed in that mode!!!

Now I want to reinstall Windows or restore from backup (some while ago, because I couldn't start Windows Update anymore and the service wouldn't run and instead of spending another 6-20 hours trying to troubleshoot that I thought I'd just restore a backup in an hour or less). But I don't know what will happen. It probably won't run and it'll be wasted time.

I *can* try to install with a 2nd disk present (as first disk) but I am afraid windows will not install AT ALL. Windows notoriously fails to install (yes, also notorious) if it is not set as the first boot device. But maybe at least it will install and run in AHCI mode this time... .

What I am going to do is try to install it on the Highpoint controller as only disk and then see if it will also run as second disk.