Freezers do well in dropping the temperature and maintaining it on a sinking load. By that, I mean an object that starts out warm, but slowly drops to the set-point of the freezer. An ice cube tray, full of water, may start out at room temperature, but it does not generate heat, once it is put in the freezer. It slowly gives up its heat until it reaches the freezers intended temperature. A device that is continuously generating more heat will overwhelm the average freezer after a short while. Most freezers, are not powerful enough to handle continuously removing the heat generated by a PC. I'm sure there is one out there that is, but it is not your typical Frigidaire.