I used Avast and windows defender for a couple of years but a few weeks ago Avast buggered up my laptop while trying to perform an auto update. I eventually managed to perform a system restore and had to remove Avast. Thought I'd try Microsoft Security Essentials instead after reading good things about it. It has inbuilt AV, anti spyware and malicious sofware removal and I have to say I'm impressed so far. Light on resources and the laptop is running faster.