Sometimes free downloads are a gamble, but one worth looking into is Spyware Blaster from Javacool Software.

Now available in version 3.5.1, Spyware Blaster has a comprehensive list of the dialers and adaware that try to insert themselves in your computer, triggered by user internet behavior that seems pedestrian enough. Spyware Blaster has modes for both Internet Explorer and Mozilla Firefox. Most users who use Mozilla still have IE on their hard drive even if they no longer prefer it. A “backdoor” to spyware could very well be that internet browser you only use occasionally and therefore more likely to be unmonitored or outdated. The software monitors itself for updates and asks permission to download them. This software has experienced no conflicts with existing dialers or applications, so most users will find it unintrusive and safe.