Defender *is* bundled in later versions of Windows. Look, far be it from me to defend M$, but as far as the free AVs go, I've recommended MSSE to a lot of my clients. It runs quietly and unobtrusively and doesn't constantly ask the user to make decisions he may not have a clue about, and it doesn't nag you to ***BUY OUR PAID VERSION ZOMFG*** every five minutes. It does its job reasonably well, albeit not perfectly, and like others I'm a little skeptical of this outfit's testing methodology and results. FWIW, out in the field servicing customers' machine I'm seeing fewer virus infections lately and more adware/crapware infections on W7+. XP is another matter. It's always been a Petri dish.