All new components desktop still randomly shuts down

[be66971baekon]

First off I work a 3rd shift so Im sorry if I don't respond soon enough. NOW to the situation. about a year ago my custom built from a company started doing random shut downs and at that point i had never touched it myself software/bios/hardware related. Now i've seen this problem allover the internet with more unsolved posts than solved, but heres what exactly is going on and what i've tried so far.
It shuts down with no bsod randomly while watching videos or playing video games at different points never consistent. when it shuts down it will not restart even after i turn off the power switch and unplug the chord and plug it back in. it usually takes 10-15mins sometimes less. what i've tried so far is used ccleaner to fix any registry errors and that seemed to make it crash a little less often but still anytime i play games. I am on my 3rd psu and have been for awhile and after attempted debugging months ago i determined its not that. I have installed a new cpu heat sink with copper piping and reapplied thermal paste that was recommended and that did drop my cpu core #0, #2 temps down which were hovering around 80 c during stress test. now they dont even break 40 degreees. but i did notice today that there was only one item around 70-75 degrees and i believe it was labeled TMIDO i think? im at work now and cant remember. other than that i have also replaced my graphics card and the problem still persist.

specs

antec 550watt psu
gigabyte motherboard with an i3-540
nvidia gtx660 graphics card
2-500gb harddisks

i can take screen shots and pictures of my set-up when off for work but for now this is what i have.
-thank you kind people of the internets

 

[Quadacon]

open windows event log, then you can see all system error, failures, warnings ect.
once you find out what is wrong example look at error codes and tell us what it sais