Ya, it's insidious. The virus I had was popping up those come-ons in new tabs, among other exciting commercial opportunities. The devils have gotten much more clever. Some of the windows looked like the microsoft web site, and a live "tech" claiming to be a microsofty instantly starts chatting to you about your computer problems.
I was very suspicious of spyhunter (their free trial only allows a scan, no removal.) But my experience with them was awesome, they are certainly legit. I've chatted with some computer geeks since my experience, and Spyhunter is first rate.