Oracle VirtualBox not showing 64 bit guest version on my 64 bit host OS.

>>Initial VitualBox Create Virtual Machine
Even though my Host OS is a 64-bit version of Windows, Virtual Box categorically refused to display any 64-bit guest OSes in the Create Virtual Machine dialog box.

>>BIOS
To solve the problem-Uninstalling and reinstalling VirtualBox made no observable difference so I booted into the BIOS and in security section enabled the Intel (R) Visualization Technology and Intel (R) VT-d Feature

Now in the create virtual machine dialog box displaying 64-bit guest OS.

 Bottom Line

If VirtualBox is only showing 32 bit versions in the Version list make sure:

 ** Your Host OS is 64-bits

 ** Intel Virtualization Technology and VT-d are both enabled in the BIOS

 ** The Hyper-V platform is disabled in your Windows Feature list (For windows 8.1)