I found that Microsoft is offering a anti-spyware software for Windows users. You can find a test report on CNET.

I installed the beta on two of my computers and did not find any spyware, this was as expected as my systems are secured by Lavasoft Ad-Aware too, but Lavasoft changed from freeware to expensive-software with limited maintenance.

Also installed on my computers is Spybot Search & Destroy, a very good piece of software which is still available for free.