You know what happened to me recently? I had downloaded an anti spyware that scans, detects and removes spy ware. In an hour it detected over 500 spyware on my little netbook I borrow from the library. It's sad that the detecting methods are not being used with a bit of common sense. It's not to arrest someone, but to arrest the guilty culprit like they do on NCIS!
I don't want to worry you overly much, but there are downloadable programs advertised as anti-spyware that are themselves spyware or what might be called fraudware, a term that I just coined as I wrote it, to describe software that warns you of things that your computer doesn't really have, then charging you to remove it. I'd stick with the well known anti spyware, anti malware, or antivirus programs, and pass on ones that don't have a good reputation.