An anti-virus really isn't a effective piece of software, I am not saying you should remove it, but souly relying on it won't work out, the definition updates take time, most threats are zero day or at least new threats. Security on a operating system is about layers. Personally my setups goes like this, keyScrambler (anti keylogger), Avira, WinPatrol (activity monitor) and sort of unrelated but I use KeePass for my accounts. I'd also suggest a firewall like Comodo however they come at the trade off off basiclly all piracy so I don't use one.