Avast free on my desktop Win7, Windows Defender on my Win8 laptop.
I don't like AV's that use BitDefender engine because they flag way too many false positives, BitDefender in general is a heavy AV engine.
I don't like AV's that use multiple AV engines, more engines equals more false positives. You can simply scan any file you download with VirusTotal before running it, there is no need to use several AV engines in real-time.
I have no reason to use paid AV's since freeware does its job for me. Other AV's that I will recommend are Avira free, AVG free, MSE and Panda Cloud free. Eset only if you want to pay.
Enjoy!!
