For those happy with Windows Defender or MSE, just because of the low maintenance and small footprint, a lot of independent security sites rank both extremely low in detection tests. Again, just because you're a knowledgeable user, doesn't make you immune.
http://www.av-test.org/en/news/news-single-view/25-internet-security-suites-are-put-to-the-test-using-windows-81/
Also, speaking of Do-Not-Track plug-ins, check out the Free, Open Source "Privacy Badger". It does a great job and is a pretty cool FOSS project in general.