Cannot boot Win10 from disk 2 while taking disk 1 with other Win10 out of computer. Dual WIN10 boot. Lack of EFI file?

Question

I have two disk at computer and I installed two Windows 10 operating systems at separate drives. Unfortunately after taking out disk 2. I cannot boot windows 10 from disk 1. It looks like windows boot manager is only at disk 2, so it prevents me to boot at WIN10 from disk 1 (lack of EFI file)? Both disks are GPT.

How to repair this?

Answer 1

Only one EFI partition is required for any number of installations, so the second installation disk didn't need it.

You will need to:

• Use both disks to boot
• Resize disk1 partitions to create unallocated space of 500 MB
• Create the EFI partition on disk1 as described in the post
  Create EFI partition before installing Windows 10
• Create Windows 10 bootable media using Media Creation Tool
• Take out disk1 and connect disk2 in its place
• Boot from the boot media and do Startup Repair
• Disk2 will now be bootable.