When you install and run a virtualized ESXi 5.x server under VMware Worstation, you will get the following message
<HARDWARE_VIRTUALIZATION WARNING: Hardware Virtualization is not a feature of the CPU, or is not enabled in the BIOS>
and when you try to turn on a 64-bit VM on that ESXi, it will fail. However, if you have an i3 CPU or newer, 64-bit virtual machines can run in a virtualized ESxi environment by eneabling virtualized hardware virtualization (how cool it sounds?). Shut down you virtual ESXi server and find its .vmx file (this is a virtual machine configuration file). You can find it usually in VM’s working directory – open virtual machine’s settings and go to Options tab. Open the file with a text editor and add the following line at its end:
vhv.enable = "TRUE"
Save the file, start the virtual ESXi. Now you can run 64-bit virtual-virtual machines