Question BIOS won't recognize M.2 that I just installed Windows 10 on with GPT partitioning

[malcolmxleigh]

I'm trying to install Windows 10 onto my M.2 that I bought a while ago and was using as just game storage but decided to switch for better speeds. I don't need to worry about backing anything up as I have a flash drive with my stuff on it. I just want to get this setup properly as I'm completely lost.

The M.2 (Western Digital SN770 1TB from Best Buy) is 100% partitioned in GPT as I did this before I left my previous windows installation (that also no longer works? Says it needs to be repaired) with Disk Manager and did again with DiskPart in cmd with the USB creation tool. After installing windows successfully and it restarting, with CSM off and Secure Boot in either Other OS or UEFI Windows I do not see my M.2 appear as a boot option. The BIOS does recognize it in general however. Once I change CSM to ENABLED or AUTO the M.2 appears as a boot option just as its name, no "UEFI:" or "Windows Boot Manager" like my USB and previous Win10 installation. I also cannot reinstall Windows with the USB on my M.2 when the BIOS has CSM on as it says the drive is in GPT partition. The old drive was also GPT.

It seems like with CSM on, it can boot off the drive but not all the way into windows because the drive is in GPT, but with CSM off, it can't see it as a bootable drive but I can install Windows on it as both are GPT/UEFI systems? Wtf do I do at this point? I read about manually creating a bootable partition which I thought I tried correctly but maybe I didn't format that right afterwards who knows.
Do I just reformat back to MBR and turn CSM on? I'd rather use the newer UEFI stuff than be held back because I don't know how to get my stuff working.

System:
Windows 10 Pro
ASUS PRIME B450M-A II
Ryzen 5 5600x at stock clock
WD SN770 1TB
KingDian 120GB
Intel 240GB (idk the model but it's MBR part. I think)
Seagate Barracuda 1TB (old boot drive)
4x8GB XLR8 DDR4 at 2133MHz (for now)
RTX 2080 Super

 

[Lutfij]

ASUS PRIME B450M-A II
What BIOS version are you on?

Windows 10 Pro
Where did you source the installer for your OS? Recreate your bootable USB installer. Then disable CSM, Fast Boot and Secure Boot in BIOS and then try and simply format the drive in the install window, without using CMD. Making sure you have no other drives hooked up to the motherboard would be key. You should install the OS in offline mode too.

 

[kerberos_20]

M2 drive needs CSM off to be bootable
you probably installed windows on it while another drive was present..so boot files are on some another drive..which is also why youre getting "this drive needs to be repaired" while booting from another drive..as you kinda borked it

either way, disconnect all drives, just keep your M2 plugged in
keep csm off
boot from usb win media, and either try repair with fixboot command in commandline or reinstall while wiping your drive

 

[malcolmxleigh]

ASUS PRIME B450M-A II
What BIOS version are you on?

Windows 10 Pro
Where did you source the installer for your OS? Recreate your bootable USB installer. Then disable CSM, Fast Boot and Secure Boot in BIOS and then try and simply format the drive in the install window, without using CMD. Making sure you have no other drives hooked up to the motherboard would be key. You should install the OS in offline mode too.

BIOS was the latest that I updated today. Version 4402 but the date for some reason does say 12/13/2023 instead of the website's 1/8/2024 but the version numbers are identical so I assume it's just the wrong date? The installer is just the media creation tool from Microsoft's website that is also the latest 2022 but I did not install that to my flash drive today, I did that a month ago for a friend technically.

For the "Secure Boot" setting, all I have is "OS Type" that I can change. "Secure boot state - Setup" and "Platform Key (PK) state - Unloaded" are both greyed out. Should I change OS Type from other OS to Window's UEFI? I did try this before from another tutorial...