My computer just started turning itself off randomly. No rhyme or reason, and no reboots. It just turns straight off like the power cord was yanked out. The PSU is an aged ~5 years, but pretty well built 850w silverstone. my board is a newer but cheaper asrock (I can look up details later). I'm leaning toward board, but I can't help but think the age of the PSU might be showing even though I've never really made it work hard.