I put a CD with Ubuntu on it in my laptop, then turn off and turn on my laptop. As it stars up, I hit the "f" buttons, and it does not bring up the bios menu I was expecting in order to boot from the CD. I tried holding the function (fn) button and hitting f1, f2, all the way to f12. I tried hitting escape, and delete. Nothing keeps it from just starting up in Windows 8 like usual. What do I do to boot from the CD?