Avast sucks, use Bitdefender
Avast is the worst antivirus I have ever used. They CONSTANTLY ask you to upgrade to premium/disc cleanup/ etc. and the worst part was that the antivirus inserted a debugger value into all of my .exe files which completely kept me from using almost all of my programs for weeks, I had to comb through my registry for hours until I was able to wipe out the issue, not to mention it is near impossible to uninstall all of avast’s files from my computer. Upon canceling my service they continued emailing me with sales and promotions even after unsubscribing from all emails. Go with bitdefender guys, it’s free, rarely asks you to upgrade, has a much less clunky and complicated UI, and it hasn’t bricked my computer like avast has. Words cannot express my hatred for this service.