windows 10 virtualbox only showing 32 bit

The BIOS in the generated Parallels 12 Windows 10 machine is generated by Parallels. but which BIOS then in my case please? The BIOS in OSX does allow virtualization per default. On some blog it is advised to 'enable virtualization on BIOS'. Of course it is easier to use the Linux machine directly but I need to do some tests in order to prepare a virtualbox linux virtual machine for both OSX AND WINDOWS10 systems (for a lecture, for students), so I need to see whether this 64 bit virtualbox linux machine is runnable from the virtualbox in OSX (it is) and from windows but I cannot load her yet because virtualbox is only showing / allowing 32bit machines - being running in the virtualized windows 10 of Parallels 12. No Hyper-V enabled on windows, Windows (under System->About) says it is a full 64bit windows 10. This windows10 pro 64bit is hosted inside a Parallels 12 instance running on an OSX Sierra Laptop (a mac book pro). VMware Workstation, PCem or VirtualBox Can I use VirtualBox on windows 10 Home edition Virtualbox VM portable on a USB stick: Can I Open An OS On VirtualBox From USB VirtualBox kernel panic with Snow Leopard 10.6.1-10.6.2 Intel/AMD made by Hazard on boot (Host is Windows 7) Problem with Virtualbox 'unsupported version 14 of data unit 'cpum. I do not own any windows Host, I am trying to use an Ubuntu linux 64bit (16.04) on a virtualbox 5.2.12 on a virtualized Windows10 pro (64bit).

Windows 10 virtualbox only showing 32 bit