Read about it here click here
Have not used it personally as I use Spysweeper by WebRoot which I find very good as it it uypdates automatically and gives real time monitoring.
For a freebie on another pc I use Ewido (less invasive if you don't like continual pop up's) plus also Spyware Blaster from Javacool.
If you look at Spysweeper, get Version 3.5 for around a tenner and it will update to latest version
more than double the price) on-line.