As a recommendation, always remove or disconnect non essential components - especially power for floppy and/or optical drives for example.
You just need your CPU, a single stick of memory and onboard graphics (preferably). You don't need a hard drive for a computer to POST as many people would think!
Normally errors of this nature are either a short (as already mentioned), the CPU needs re-seating or your board is duff.
Before you buy a new motherboard (in a worse case scenario), take the motherboard out and place it on some cardboard. If it doesn't work at this point, I would say more than likely it's duff.
The other possibility (although this is incredibly rare) is a duff CPU. I've only ever seen a duff CPU once and that was three years ago from memory!
if you look in the bios the temp will rise to 120c rapidly and then cuts out but if you take the fan off once it cuts out the cpu is cold to the touch and so is the heatsink
So it is POSTing which is good, but as you say, the power cutting out is to do with the excessive reporting of the CPU temp.
It sounds like it's a fault with the board. It's going to be difficult to resolve or flash the BIOS.