Hi, I have a HP Pavilion P6000 Series Model # p6516f that during last use, randomly "shut down" on it's own. Really, it went to sleep, although I was using it at the time, but it only went black, so I manually shut it down.. ie. held the power button till it turned off. Now, when trying to start it, it comes up with only a black screen with a white blinking line... LINE, not cursor, on the top left corner. I checked all the external things, the prongs, the cables, every simple thing, and it's still doing it. Please help.