[SOLVED] Why won't windows boot off my m.2 ssd?

[Gamma1440p]

Alright... So I recently built a new pc and transferred old drives to my new build. The old drives in question are a 1tb wd black mass storage hard drive, and about a 250gb ssd which I used for the operating system in my old build. I attempted to use that ssd as my operating system, but quickly regretted that.

I eventually did a new install of windows 10 on my new m.2 ssd. The pc booted up and I was able to fresh install windows 10. But... This drive can not be left alone. For some strange reason, I must have the old ssd (with nothing on it after a format) set as the first boot device, or my system won't read windows 10 off of my new m.2 ssd. If I unplug the other drives, the same thing happens. Windows can't manage to find the operating system, on the only drive that has the operating system. When they're both plugged in, I must choose the m.2 to boot windows from a blue windows screen.

I've never had a problem like this before. I've tried to mess around with my boot setting and couldn't find a solution. Nothing I've read online thus far has helped resolve the issue. One thing to note, is that my old ssd is labelled "windows boot manager" in my bios. I have an idea that this might be causing the problem? Maybe not. I've only been playing around with this stuff for about a year now, so I have a lot to learn.

My build

Motherboard-Asus rog strix x470-f
Power supply-Seasonic focus 750w 80+ gold
M.2 drive-Adata xpg sx8200 pro 1tb
SSD-250gb (Dont know the brand)
Hard Drive-WDBlack 1tb 7200 rpm
GPU- Zotac 2070 Super 8gb mini
CPU-Ryzen 7 3700x
Case-NZXT H510i

 

[USAFRet]

Did you install the OS on the new drive, with only that drive connected?
If you had other drives in there during the install, the boot partition ended up on one of the others.

That is why you must have only the one drive connected when you do the install.

If this is a brand new install, just redo it.

How To - Windows 10 clean install tutorial

If you are looking for the Windows 11 Clean install tutorial, you can find that here: Windows 11 Clean install tutorial (Click here) Otherwise, welcome to the Windows 10 Clean install tutorial This tutorial is intended to help you, step by step, to perform a clean install of Windows...

forums.tomshardware.com

 

[Nemesia]

If you already have windows on the other SSD, when you install it to the SSD you want the OS on it often doesn't set up the bootloader on the drives you want and just uses the one from the other drives, so if you ever remove the other SDD from the system at a later time, the main SSD is unable to boot without running some repairs that are a pain.

Or what USAFret said will happen too even if the other drive does not have an OS installed on it.