Second, VirtualBox allows any ISO to be mounted as though it was native by using the Virtual Media Manager. The Windows VM should treat the ISO file as a physical disc, thus allowing it to be ...

Also looking inside the memtest86-iso.iso file, I don't see anything I recognise as characteristic of bootable media e.g. it doesn't look like a linux bootable or a windows bootable..

Enable Drag and Drop support in VirtualBox Drag and Drop feature allows the user to copy a file from the guest computer and paste it to the host system and vice-versa.

If you deploy virtual machines with VirtualBox, you'll want to use the shared folder feature. Find out how this is done in VirtualBox 7.