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?

You will have to create the EFI partition on Disk 1. What have you attempted to perform that task? There is a great deal of documentation on how to accomplish that task. — Ramhound, Nov 02 '19 at 17:10
Is it ok if I create EFI partition as third or fourth partition, not first in line? — lluke, Nov 04 '19 at 09:54

score 0 · Answer 1 · answered Nov 02 '19 at 20:25

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.

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

1 Answers1