Question – PC Won’t boot windows after changing secondary drive

So, what has likely happened is that the EFI boot partition on your other drive was likely recognized by the Windows installer when you did the installation on your newer drive so it did not create a new one on the new drive. Now that you’ve removed it, Windows has no idea how to boot.

This is why it is recommended to remove ALL other drives when installing Windows, and it is likely that you will need to again do a clean install of Windows on that drive but this time do so with no other drives attached to the system except for the drive you are installing Windows TO and the drive you are installing Windows FROM, which typically would be a USB flash drive these days.