According to a distressingly common urban legend, some law of logic holds that you can't prove a negative. A little reading in philosophy would show that no such law of logic exists. For one thing, how would you go about proving that you can't prove a negative, since the statement that you'd have to prove is itself a negative?
Moreover, as a practical matter, we prove negatives all the time. I routinely have to do so in my job. Typically, disproving a proposition B requires nothing more than submitting A into evidence, where A => ~B.
(Oops, my bad -- We're supposed to be talking about Lady Gaga now, aren't we?)