Check this out... _http://www.flexbeta.net/main/articles.php?action=show&id=39
It shows that "The objects or problems that Spybot S&D failed to detect were more than twice as many as Ad-aware’s. Ad-aware not only proved to be able to find more infected objects, but has superior usability. Ad-aware also has a very active
support forum with over 41,000 members and more than 144,000 posts. Spybot S&D also has a
support forum, though I wasn’t able to determine how active it was since several attempts to connect to the website failed. However, you are able to contact
Spybot S&D support by sending an email. However, sending an email to a specific person for support (even if it’s a team) is not as effective as a forum where thousands of members can leave documented suggestions. Though Ad-aware proved to be a more effective tool for detecting spyware and adware, I believe no tool is more efficient than having the general knowledge to be able to determine which programs are going to infect your computer with malicious files."