Old thread but just to clear things up, RealTemp does not adjust your core voltage during its CPU Cool Down Test. Randomizer is correct. It adjusts the Clock Modulation feature of the Intel processor. Do a Google to find out more about what this does.
I've run this test many times without ever having a problem or my computer freezing up. If your computer is not stable during this test then it is likely that your overclocked CPU is not 100% stable.