satellite l850d won't boot from usb,even bios is set to boot from usb

[Harv1]

I have ubuntu 12.04 installed,I am trying to boot into zorin os 8 on a usb stick.bios is set to boot from usb but it doesn't it goes straight into ubuntu and loads .It works great on my acer.don't know what else to do.Please help?

 

[armapker]

Are you plugging into a USB 3.0 port? if so try a USB 2.0 port and it will probably work. If not just burn the ISO to a DVD, it's not as convenient but it will work