I’m recently trying to my migrate my pc to a new case. This new case won’t be able to support one of my HDDs so I’m transferring the data and ditching it. After unplugging it my pc refuses to boot. Plugging it back in makes everything back to normal.

Why?

I have my NVMe as my only bootable device with windows on it and it doesn’t want to boot it. This HDD doesn’t even have windows on it and it lets me boot. It’s NOT booting from the HDD because in Disk Management it says the NVMe is the Boot Drive. I have theories as to why it’s having issues.

1. This HDD was from my first pc a long time ago with it being the only drive and having windows on it. Even though it no longer does. I cleaned the windows files from it but didn’t clean the whole drive.

2. My PC is still on legacy BIOS but I believe at some point I may have switched this drive to UEFI. So maybe the bios is confused?

I have no idea how to tell what the issue is and where to start. It is on Windows 10. I can’t upgrade to 11 because I have issues with MBRtoGPT(which is a whole different issue I need to fix). What settings can I change to fix this.

I have a larger and faster NVMe that I can clone to from my old NVMe but will that fix it? 

I’m fine with reinstalling windows 10 on the new NVMe but why is this HDD stopping the boot?

I’ve gone through every folder on the HDD and it’s all just copied game files and old music.

Why does removing this drive stop my pc from booting?