Install 64-bit Operating System as a VirtualBox Guest

You have installed VirtualBox, you have an ISO ready to install 64-bit Ubunto, FreeBSD, or your favourite OS, but when you try to create a new VM, 32-bits is the only option.

You may have searched, only to find that everyone says you need to turn virtualization on in your BIOS, but you checked, and you know it's turned on.

Try this: reboot.

Yes, a single reboot, and VirtualBox will offer to create 64-bit VMs.