Intel dq57tm with i3 530Update your post to include full system hardware specs and OS.
Provide more description about what happens when you turn on the pc: any beeps, any leds, any clicks, etc.....
Provide more detail about the problems that led you to change the snowman to stock cooler.
Open the case and make sure that some internal cable has not come loose.
More information needed.
Yes gd900 and evenly spreaded itCPU: did you apply new thermal paste? What brand and how did you apply the paste?
I have checked psu with my ace psu which was 500wMy first thought is a thermal shutdown.
Reapply the thermal paste.
https://csgopedia.com/the-best-thermal-paste-to-use/
Second thought - psu. Get another psu: name brand, 600 watts.