When your computer has been noisy, overheating and slow for a while and now:
> when your Mac or PC starts and works but displays particles or discolorations on the screen,
> when playing your game it randomly cuts off and restarts the Windows,
> when you can power your Macbook up and then go to edit some photos or movie and it cuts off or the display stops working,
> when starting your mac it displays the progress bar and seem frozen indefinitely
> when starting your Mac or PC and it makes all the normal noises, blinks the lights but the screen does not come up at all
You might need the reflow service which would involve taking the computer apart, reheating the motherboard so the video chip would solder itself back properly onto hundreds of connection points to communicate with the motherboard correctly again. In the worst cases it might be required to take the VGA chip off completely, replace those hundreds of tiny solder balls connecting the chip to the motherboard and then reflowing the chip back in place.