Ok about 1 month i had been working on my moms pc i had replaced the hard with one of my extras till i could get her a new one,well i was in the middle of doing some final driver installs and setups,and out of no where the pc freezes for half a second and then the screen goes blank and it was off,i tried to turn it on,and NOTHING happened when i pushed the power button,i had checked all the cables inside and none were lose.
I then gave up and said it was the psu ,and then have been waiting till i can afford to get her a new one.
Then eariler today i was in the room talking with my mom,and out of bordem(and ADHD lol) i pressed the power button,thinking nothing would happen,but for some weird reason it powered up and booted just fine.
I have never heard of a PSU dying and coming back to life lol.
Could also be a short in the Power button or wires, I've had that problem when in damp environments when it some times would just shut off or auto turn on. Still got a case that has that problem behind me being used as a Nightstand/snack shelf.
your psu is now 400watt, your gpu needs atleast 400 and your cpu 65 watt, thats a total of 465 watt. i would recommend atleast a 500 watt psu. this thing is going to sweat and kill itself especially becouse it has crap components also always have about 15% more power than your build needs.