If VirtualBox is not booting from ISO or if GParted ISO is not mounting, correct the Boot Order in System Settings and verify the ISO Attachment in Storage Settings.

In order to rule out that it's not an issue with that physical computer and in order for the thing to be reproducable, i thought of trying it in a Virtual Machine 'cos if anybody here could get it ...

VMware can install a guest operating system either from a physical disc drive or an international standard for organization image, which is also referred to as a disc ...