panseluta

It's a little late for this answer but here it is:

when your processor is overheating you can lose power without any warnings. you can start the computer after that and lose power again in a few minutes. in this case you have to clean the processor (also to replace the paste) and clean the fan.

In your case you lose power randomly wich has nothing to do with overheating or memory or HDD.

It's a malfunctional AC Adapter!
That little thing made me waste one night trying all kinds of tests with no result.