ya, sooner or later it will return into it's gazeous existance cause CO2 is only in the ice form if you take it to a very low temp. if ya go over this temp, it begins to melt and become gas, but during this process (as your physics teacher can explain to you more accurate) it takes power (in form of heat) from its surrounding, so it can be used to cool a cpu, but not as final solution like a watercooling or vapochill, this probably only works if ya mobo is lying flat and the frozen CO2 is put in a heatconducting box that is put onto the cpu