Microsoft Antispyware Beta. It's free for now because it's in Beta for you to try. Another good one is Sun Belt's Counterspy. They look almost exactly like each other, and at the same time, these are two of the best antispyware available. Counterpsy, you have to pay for. It's very good and worth the money.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?