Spyware is the most widespread security threat to Windows-based computer users today. Depending on who you talk to, and how they define spyware, the vast majority of PC-users have some form of spyware on their computer. If you include cookies, we all do.
Now you're probably thinking almost everybody, but not me! Let me reiterate. If you have never switched your computer on and you live alone, you don't have any spyware on your computer. Everyone else pretty much does.
And a word to those people (men: pay attention) that spend time on free websites that feature pictures of naked peoplethat's a great place to get spyware, especially the drive-by download kind.