When you start a virtual machine with VirtualBox, the following error message :
"The VT-x/AMD-V hardware virtualization is not available on your system. Certain guests (eg OS / 2 and QNX) require this feature to be able to start".
This error simply because your processor does not support virtualization or that it is not enabled in the BIOS of your motherboard.
For information : All new processors support virtualization (VT-x Intel and AMD-V for AMD) but motherboard manufacturers do not always enable this feature by default.
Simply turn the virtualization of the processor (CPU) in the BIOS of your motherboard. To do this, follow our tutorial : "BIOS - Enable virtualization (Intel VT-x / AMD-V)".