A few years ago I replaced the PSU in my son's computer. At the time I didn't have a lot of money for a replacement so I purchased a generic power supply for about 25 Euros. About a week after the install, my son was sitting at his desk when he heard a loud bang. Later he told me it sounded like a firecracker. immediately following the small explosion, smoke rose out of the back of his desk. When I came into the room small flames were jumping out of the back and side vents of the case. I quickly hit the breaker, disconnected the PC and tossed it out onto his balcony. After that I poured bottled water into every orifice I could find. I should have known better than to buy a cheap, no name power supply.
Needless to say, I'm extremely grateful that nothing happened to my son ... he usually falls asleep with the PC on.