There's no way there won't be condensation on the motherboard, i want to hear from treetop again. He's the one who didnt' use any dielectric grease right? It would take a butt-load of baking soda to convince me it would work. Also, you better not open that fridge very often, and the tip about not turning off the computer will help too.
Hard drives don't like being put in the cold, i think 45*F is the lowest recommended, or something like that.
Now that I think about it, how powerful is the fridge? It's possible that the heat from the computer will overpower it, which kills any discussion of condensation.