Problem scenario: Using Oracle VirtualBox on a 64 bit version of Windows, you go to create a new virtual machine as a guest server. You want it to run a 64 bit version of Linux. You start to build the new machine using Oracle VirtualBox. You choose the "Version" and only see 32 bit options. You have a processor (hardware) that is 64 bit. The Windows OS is 64 bit. But you do not see 64 bit options for the OS choices. How do you install a 64 bit version of Linux as a guest server?
Enable VT-x (Virtual Technology VTx) in the BIOS. One example of how to do this is here (but it is for an HP Probook only).