My computer keeps randomly shutting off, and, while a big annoyance, especially in the middle of competitive games, I'm afraid something serious is wrong with it. It doesn't close all my open applications then slowly turn off like I've clicked "Shutdown," but it instantly turns completely off and makes the little hum sound, just like it does when the power dies. My brother said that he's checked the cords and they're plugged in tight, so I'm not sure what's going on. Does anyone have any idea what the problem could be, and how I could go about fixing it?