I had my HDD partitioned for XP and having VM (or whatever it is); having not used Windows in over 5 months, my new hard drive has nothing on it for running Widows as having it is kind of lost space at this point. I used to use it as some programs I used were not OSX compatible, but that's changed and so Windows are something I look out of in my office and wonder what it is like to stand in the sun and not under fluorescent tubes.
I have an office desktop with Windows and they issue a laptop which is Windows as well; I haven't used either in so long I honestly do not know what version of Windows is on them. Oddly enough, when I got my MBP I liked the hardware design and figured I'd Windows almost all the time, but I took such a liking to SL that it was the exact opposite.
10 years on windows and no virus? Wrong. Level playing field or not, OSX has been out for 10 years and still no viruses.
I know people who have ran Windows for years without virus software and have not had issues. Obviously, compromised websites, emails, links, and Rick Rolling are the usual culprits and so avoiding them reduces your odds of viruses considerably.
Most anti-adware programs also frequently identify files that have no harm and are for the user's convenience, but identifying them as spyware makes the program look more efficient.
Mac users often state the lack of viruses as such an advantage and it makes me wonder what websites they are visiting to be so worried about them? Most people here also know how to avoid viruses so they probably go longer clean-intervals than a basic user.