P2P sites can be the source of a lot of this kind of stuff too. If the actual program doesn't install spyware, then it's a fair bet that some of what you download will contain trojans.

I recently acquired Trend Micro and I think it's excellent. Unfortunately it isn't free, and I'm currently on a 30 day trial. I also have Spybot and Adaware, but went looking for Trend Micro (or something similar) when Adaware "froze" during every single scan. This happens with both the paid for and the free version and not always during the same part of the scan. It's annoying and illogical like so many things to do with computers, and easier just to find a different program.