Laptop will not boot OS or BIOS?

OK, so this morning, I woke up and turned my Toshiba Satellite a505-s6965 laptop on, and left the room. I have a dual boot, so it boots to the grub menu, and after 10 seconds, automatically loads to linux. When I came in, it was loading to linux, so I pushed the power button and turned it off, as I have done countless times. Then, when I turned the computer on, the computer loaded past the option to load BIOS, and then got to a black screen, with a little white underscore in the top right corner, this normally does this, but now it was not blinking. I waited 5 minutes, still the same thing. I restarted and tried to load BIOS, by pressing F2, as it says, but this does not respond, and it goes back to the black screen. I took out my Ubuntu LiveCD, and popped it in, and tried to load it from that, still nothing. This, was where I was assuming that the HDD got messed up. That did not work, so I went to an identical a505-s6965 and swapped out hard drives. The working laptop loaded all my files without a problem, and the broken laptop would not load the files of the working one, with out doing the same thing. So, what could my problem be?