Others may have specific reasons for needing third party security but I find that the Windows firewall plus Microsoft Security Essentials gives me all the protection I need. My interne use is quite far reaching and I have had no malware problems at all.
I have no use for MacAfee or Norton in personal PCs or laptops; have removed them from many client's machines, over the years. Remove it & use MSE... extremely good, A-V & A-M in one, not resource-demanding, fully automated, no annual renewal rituals & 100% FREE. I did use & recommend Avast BUT, only prior to the arrival of MSE. Other good but, not absolutely necessary, things are Malwarebytes, SpywareBlaster, BrowserGuard & CCleaner.