My hard drive died and so I decided to run Ubuntu 12.04 from a USB. It ran flawlessly for a while, then suddenly it crashed and now when I start the laptop it says "Operating System Not Found". I do not have the hard drive in the laptop and I never did when I was running Ubuntu. I have set to boot the USB key first in the bios and I have used the USB on other laptops and it works.
I have an Acer 5536G. I would be very happy if I can get any help. thanks