I Came over to Avast Free way back in 2006 after being a tester for Windows Live Onecare, and I guess I did more risky things then as severely infected my old system way back then, While Avast couldn't clean it at the time, was a boot sector virus, something in the bios then as well, shop ended up having to build me a whole replacement system with slightly lesser specs than original as had no warranty at the time, then again warranty may not have covered it.
Always liked Avast Free for it's protection, speed, and not doing anything bad with system performance either.
At the time Shop didn't recommend Avast, but I ignored there recommendation to use Symantec Norton as I felt safe with Avast, and to this day still do for all the systems, and Phone as well, sure have to put up with more ads, watching what I click when i boot PC, and when doing scans in order to keep the free version, it's not about money these days why i stay with free version, i feel i don't need all the Internet Security, Premier and Ultimate versions of Avast features to protect me, and such