Spybot - Search & Destroy

Like Ad-Aware, Spybot - Search & Destroy has played a prominent role in the history of the Great Spyware War. Also like Ad-Aware, it's completely free. Spybot, however, boasts a number of convenient extras, such as a full-fledged scheduler and a file shredder. It's also no slouch when it comes to sniffing out malicious software. We should note that when it comes to antispyware utilities, you can never have too many, so you may want to load up on a few more freebies, including Microsoft AntiSpyware and Spyware Doctor.