I have Xoftspy. It cost about $40, but it is well worth the money. They stay on the ball with frequent updates.
I had Spybot and was still having trouble. I was shocked at what all was on my computer that Xoftspy found that Spybot didn't. There was somewhere around a hundred different things Xoftspy got rid of and I haven't had any problems since. What's really cool is if it is something that might screw up your computer if it is removed, this stuff recognizes it and lets you know, so you aren't shooting in the dark.
Like I said, it's not free, but in my opinion it has been more than worth the $40 I spent on it.