Dont use AVG or Avast. Those antiviruses areshit.
I would recommand Nod32 + zone alarm firewall. Antiviruses like Kaspersky or BitDeffender are great but they use alot of CPU, Nod32 doesnt use alot of CPU so your computer wont lag or anything.
Also you can download Malware byte's the antimalware, scan your pc every 2 weeks with malware bytes and you wont have any viruses ;)
Anyproblems, PM me, I've been working with tools like Combo fix or HiJackthis for a long time =)