I reinstalled my work laptop about 6 months ago (XP pro).
I set it up with Firefox and Windows Defender (upgraded from MS anti-spyware beta at some point).
Since then I have done a lot of web surfing, ranging far and wide, not visiting any sites obviously dodgy, but taking in a lot of different websites all the same.
Today, out of interest, I loaded up and scanned with Spybot Search and Destroy for a second opinion about the state of spyware on my machine, and all that was found was about 5 tracking cookies. And that was all!!!
I was really impressed as I wouldn’t have been surprised if something had slipped through.
So these two apps have worked very well in partnership for me, recommend them to anyone.
One key thing was that they were installed immediately onto a fresh install of windows, which seems much easier to protect than to clean.