|I remember this used to happen regularly on an old laptop I no longer have - a single "click" sound and then it would just turn itself off.|
I put it down to either a failing hard drive or overheating. I tested the drive with the drive maker's diagnostics - passed okay.
Didn't want to spend any money on it since it was very low spec & ancient, so never did prove that overheating was definitley the cause, but I was 99% sure.
I often used it on my lap without a tray or board under it, which is known to be bad practice as it blocks the air vents underneath, so yet more reason for me to suspect overheating was triggering the thermal protection circuit-breaker inside the laptop case (hence the click).
However, if you want to be sure it is not the hard drive that's making the click, test it with "Seagate SeaTools" (it can be used to test both Seagate and non-Seagate drives): http://www.seagate.com/support/down...