motherboard dead?

I am trying to build a computer with the old parts I own but when I turn the pc on it only stays on for about 5 seconds then powers off then turns back on then back off again in a cycle. The parts are 4 to 5 years old but when I built my new pc about 7 months ago the parts were working perfectly...

From the start: TLDR below. So pretty much I built a pc for my little brother, it was working fine for a week or so maybe. Then my little brother left GTA running overnight by accident, and I woke up and I had to change the cords around or it would just turn on, but the screen wouldn't, no bios...