Question Really weird install issue, Windows 10 installing boot partition on different drive

Oct 5, 2019
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New build, with an ASRock Taichi x570 board, latest bios. Sorry, this is a bit long, want to include everything that happened.

So at first I just replaced my MB, CPU, and RAM, and put my old HD in there and fired it up. It worked, but of course I wanted to do a clean install shortly thereafter. So I did, on my new NVME M.2 drive. Everything worked, great. Until I wiped my old drive. At which point the PC refused to boot. I tried running startup repair from windows install, no luck. It appeared that the boot partition on my original drive was being used to handle booting, which I thought was weird since I did a clean install from a fresh download from MS, onto a USB stick. I ran the install from there, onto the new NVME drive which was blank, no partitions or anything.

So whatever, it was a new install so I just did it again. This time the old HD had been wiped, it was totally empty. And Windows did the same thing again. Single partition on the NVME with the Windows install, boot partition on the old HD. Both drives were wiped before install, and I simply pointed Windows at the NVME drive. Never created partitions or did anything with the old HD, and yet during install Windows slapped the boot partition over there. So now if I disconnect the old HD my system won't boot again. What the actual **** is going on?

For some reason it setup the new NVME drive as MBR instead of GPT. But my old HD is also MBR, didn't think that would really matter, although I am surprised it doesn't seem to think the new drive can do GPT. In disk management the new NVME drive has a single partition, marked as "healthy, (boot, active, crash dump, primary partition)". The old HD has a 579MB partition marked "healthy (system, active, primary partition)". That was all created by Windows 10 install.

I just want a clean install on my NVME drive that will boot all by itself. I know, the next logical step is to remove all drives except that one and install to it, but I kinda want to know why it's doing this and I'd rather not do a third fresh install now that I've got things setup yet again.

Thanks, sorry for the wall of text.
 

gardenman

Admirable
Herald
Welcome to the forums!

This is a known issue here in these forums. We always recommend people to unplug all drives except the one that you want to install to, or else you will have this problem. Boot partition on 2nd drive, Windows on main drive. I don't know why it happens, it could be order of drives to the motherboard or some other issue.

the next logical step is to remove all drives except that one and install to it
That's correct. The only way around it is to unplug all other drives, install Windows, plug the additional drives back in.

Another thread for you:
 

Math Geek

Champion
Herald
since you had a working bootable drive installed, windows defaults to those boot partitions. so you basically made a dual boot system by putting a new OS onto the new ssd this way.

unplug all drives but the new one, reinstall and then reattach the old one once it is all up and running.

you should also make sure the boot priority is set to the new drive otherwise it will simply re-find the old one and boot to that like it used to. once the second drive is back in you can delete the boot partitions from that one or format the whole thing to make it a pure data drive.

i recommend a full quick format to be sure nothing windows related is left to mess with the new install on the other drive but you can get away with deleting the partitions and then the windows/program files folders. though it sounds like you already did this part
 
Oct 5, 2019
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Math Geek, I did all that, didn't work. Windows just decided all on it's own to create a boot partition on a different drive during install.

I tried this from an elevated command prompt. "bcdboot c:\windows /s c:" That actually worked, I was then able to disconnect the unwanted drive and Windows booted solely from the C: drive. Yay.

I reinstalled anyway because I decided I wanted my boot drive to be GPT. So I converted it to GPT with AOMEI (from a usb boot) and installed Windows. Annnnd of course, Windows converted the drive back to MBR before installing. sigh

I think the issue here is I have some older MBR drives attached, so the BIOS defaulted to compatibility mode. Then I tried to install Windows on a MBR drive while there were GPT drives available with unallocated space. So Windows wanted that UEFI boot partition and put it on a GPT drive, which of course wasn't my boot drive. I fixed this behavior by making sure none of my drives had unallocated space, except for the one I was installing Windows on. Then it worked, except Windows insisted on making that boot drive MBR again. Which I guess is simply what it does unless you're booting into a UEFI bios without compatibility mode enabled. But yeah, you don't have to completely disconnect all other drives, just make sure they don't have any unallocated space for Windows to play with.

Now deciding if I want to fix this by moving data, wiping and converting my MBR discs so I can have a pure GPT system. Super annoying.
 

Math Geek

Champion
Herald
you missing the main part here. there should be no other hdd's plugged into the system during the windows install. then windows won't "just decided all on it's own to create a boot partition on a different drive during install "

there will be no other drive there, so windows will have to all be in one place on that single drive. literally, unplug EVERY other drive from the system except for the ONE you wish for windows to be installed on. only plug the others back in once windows is installed, running, configured, updated and so on and so on.
 

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