Kali Linux 2.0 USB Boot (Help)

Hi there fellow hackers, I am currently having trouble installing Kali Linux 2.0 onto usb...

So I have currently installed the Kali 2.0 64bit (as my system is 64bit)

Next I have used Win32 Disk Imager to get the .iso onto a 8gb usb

Then I plug in my usb, and power my laptop on

Press F12 to change boot order to boot from usb first

It then boots into the Kali menu

As I am planning to run Kali on live

I press live, and all runs smoothly..

Until it hits this part where it says

"kernel panic-not syncing: VFS: unable to mount root fs on

unknown block(0,0)"

What am I doing wrong? Or what can I do to fix this?

Thanks.