On the chance that the problem is caused by overheating.
After disconnecting the power supply, remove the fan from the top of the processor and carefully check for any dust inbetween the fins.
The easiest way to do this is wirh a plastic cocktail stick to remove the bulk of the dust and then a can of compressed air to remove the rest.
Replace fan and reconnect fan power supply.
As you was rendering a video at the time,there is apossibiity that the graphis card has been overloladed and failed.If your motherboard has a build in graphics socket,try using that to see if the computer will start.