Computer overheating

[soundtest]

My power supply went through that phase for a few months, then one day I came home and noticed my computer was shut down (I never shut down my PC). I pushed power and nothing happened, so I took apart the case, cleaned out some dust, and powered it up again. It powered up, but I heard a crazy high pitched noise and (retardedly) stuck my head into the case to see where it was coming from. There was a huge spark from the power supply followed by smoke and the smell of melted plastic. Luckily, none of the other components were damaged and I just bought a new power supply.