Second o/s missing from boot menu

[41donwb41]

I have / had Windows 7 Pro installed on an internal hard drive (C) on my desktop PC.
Using EaseUS Partition Master I created a System Backup (Image) of my C drive on an external hard drive as destination.
I also created a “WinPE Emergency Disk” on a DVD.
I then installed Windows 10 Pro Free (being a user of a paid version of Windows 7 Pro).
This was successful.
I then used the WinPE Emergency Disk to boot the PC.
I selected the above image to create a Windows 7 installation on a second empty internal hard drive.
All this appeared successful. The install completed OK.
But when I re-booted the PC it booted straight to Windows 10, when I had expected to see a dual boot option.
As far as I can see, the Windows 7 install on the second hard drive produced the following partitions.

1. 100 MB Fat 32 containing 2 folders EFI and BOOT
2. 1’9 MB Unallocated, empty
3. 223.1 GB NTFS containing the Win 7 o/s
4. 223.1 GB Unallocated

So, I’m surprised that the new Windows 7 install is not available in the boot menu, as the result does seem as if it should be bootable.
Also in MSCONFIC, only Windows 10 is shown under the boot tab.
I’ve looked in the BIOS to see if I can force the PC to boot from the hard drive containing the Windows 7 o/s, but hard drives appear to be lumped together.
I would appreciate any help, assistance, advice or suggestions.