VirtualBox: 'Could not read from the boot medium'

I have recently installed VirtualBox on my Mac and am trying to install Windows 7 on it. I have done this a couple times in the past alas it has not been for several years.

I was originally getting an error when booting my VB machine (although I forget what the error message was) which meant that I had to change the boot order so that Optical was at the top:

Now however, I am getting the following error when booting:

Could not read from the boot medium! System halted

I had a look on YouTube and believe that I need to edit the following settings:

However I'm not sure what settings to go for in terms of my machine.

Solution 1:

Change SATA controller to IDE controller and right click on the IDE controller to get the option: add "optical drive" to pop up, select it & move to thw right to select the iso image.

Solution 2:

Today I installed Kubuntu20.10 on an external usb disk (encrypted, lvm) and also got the same error message.

For me changing the Bios settings to EFI standard solved the problem.

Solution 3:

For me the solution was to switch from SATA controller to IDE using the same vdi disk image. I tried all settings I could imagine after doing the usual Google search but nothing got rid of the boot error.