I installed Microsoft's new Anti-Spyware program yesterday (
http://www.microsoft.com/athome/security/spyware/software/default.mspx), and so far I am impressed. They purchased another company (Great Giant?) and have been re-working their product.
Some nice features include their "System Explorers", which allow you to view things that you would normally have to use several other programs to get at, such as startup processes, browser helper objects, and even shell execute hooks.
It also runs in the background to monitor installations for possible problems. I just installed Acrobat Pro and I received several pop-ups informing me of the changes that were being made and allowed. The software knew about Adobe, so therefore allowed them. I am guessing that if it didn't know what the software was it would ask what I wanted to do, and if it knew that it was SpyWare it would block it immediately.
We'll see how things progress. Hopefully MS will make this a free download. I would imagine that if they attempt to include it with Windows they will face lawsuits from other anti-Spyware companies, so that probably won't happen.