SpyBot-S&D searches your hard drive for so-called spy- or adbots; little modules that are responsible for the ads many programs display. But many of these modules also transmit information about your surfing behaviour and more to the net.
If SpyBot-S&D finds such modules, it can remove them - or replace them with empty dummies in case their host software won't run with its bot removed. In most cases, the host still runs fine after removing the bot.
Download: SpyBot-Search & Destroy 1.3 Final