I have both Spy Sweeper and MS Antispyware, which have these brief comparison features: - Resident real-time scanner memory load of MS AS is about 17 MB. - Resident real-time scanner memory load of Spy Sweeper is about 27 MB. - SpySweeper incorporates the 'Shields' concept - MS AS does not. - Some of the enabled 'Shields' remain effective even when Spy Sweeper is shut down. I'm currently running this combination: - SpySweeper 'Common Ads Shield' was enabled, and Spy Sweeper shut down. - Only MS AS is configured to run at Windows startup. The results: - MS AS real-time scanner is enabled, with it's light memory load. - Whenever a site ad is detected, the Spy Sweeper 'Common Ads Shield' is triggered, killing the ad - even though Spy Sweeper is not resident in memory. Other combinations are possible, though not all Spy Sweeper 'Shields' remain effective when Spy Sweeper is shut down. I found this interesting - hope you do too.