Help! Storage acting strange!

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I just finished my first computer. Every component works, but something strange is happening. I have installed Windows 10 on my SSD (Samsung PM871), but it doesn't show up in the boot priority menu (MSI B350 PC MATE). Only my HDD (WD Blue 1TB) does. When I'm all booted, only my SSD is available through the file manager. When I open my device manager, it says the HDD is connected and I have the latest drivers and everything. Does anyone have an idea how to fix this?
Also, when I change my BIOS settings from RAID to AHCI, it boots. When I change back to RAID, it doesn't (INACCESSIBLE_BOOT_DEVICE).

 

Edit: I've tried partitioning the drive. It says it already is.

[Ashley MLP Fangirl]

so you can boot from the ssd, but it doesn't show up?

is it possible Windows installed the boot loader to your hdd?

[NelizMastr]

Not booting when switching SATA mode from AHCI to RAID and vice versa would be normal behaviour. Install in one mode and never touch the setting again, that's how it's designed.

 

I'm with @firelighter487 here that your EFI partition with the bootloader is installed on the HDD instead, which is why it won't show up in the UEFI boot menu.

[discountlink]

@NelizMastr could you explain how I can fix this? I'm new to this whole troubleshooting thing.

[discountlink]

@NelizMastr I've done some research. I have to do a new install, right?

[NelizMastr]

5 minutes ago, Sizeyu said:

@NelizMastr I've done some research. I have to do a new install, right?

In theory, you could create a new EFI partition and copy from HDD to SSD, but I think it would be a better idea to reinstall with the HDD disconnected, yes.

[discountlink]

Thank you very much for your help, I appreciate it. Have a nice day!