decent anti virus program

I used Avira but I got sick of the fact that it kept spamming me with ads at the worst possible times. I'm in the same boat.

Avast! was the least intrusive out of the free ones, but something about the UI made it seem a bit convoluted and cheap. Lots of false positives.
 
I've been using Trend Micro since 2007. I've tried Avira, AVG and many more, but Trend Micro was the only one that was really effective IMO.
 
There are certain things I'm willing to pay for, and comprehensive, effective internet protection is one of 'em - Kaspersky Internet Security Suite here! (from the homework I did, Kaspersky seemed like the best balance between effectiveness and resource consumption, and it's worked great so far!) Of course, I supplement it with SuperAntiSpyware (which I bought for all of $10 so I could schedule scans, though there is a free version) and Spyware Blaster
 
Get the paid version of Malwarebytes' Anti-malware. In my experience (professionally repairing PCs for going on six years), malwarebytes is the best program available. Technically it's for spyware, malware, and rootkits, but it catches trojans and viruses better than most actual antiviruses. It's very light on resources, so you could pair it with a free antivirus like AVG or Avira.

http://www.malwarebytes.org/mbam.php
 
+1 for MalwareBytes.

I currently use Avira as my main antivirus but I check anything and everything with MalwareBytes (the free version is not a real-time scanner, so it'll only pick up things you scan).

I trusted Avast once. Spent 7 hours getting rid of a virus that it didn't detect.
I trusted AVG once. I got a virus and I still don't know how, I had to completely reformat my computer.
 
Get the paid version of Malwarebytes' Anti-malware. In my experience (professionally repairing PCs for going on six years), malwarebytes is the best program available. Technically it's for spyware, malware, and rootkits, but it catches trojans and viruses better than most actual antiviruses. It's very light on resources, so you could pair it with a free antivirus like AVG or Avira.

http://www.malwarebytes.org/mbam.php

Very nice. Checking it out now.

Granted, I haven't really had virus or spyware issues since I bought this PC, it never hurts to have something low-resource guarding in the background.
 
I have never used antivirus on my PCs. (Mainly use MAC though.) But I do have two PCs and have never used antivirus and have never had a virus ever.

How do you know?

A virus isn't always an obvious system-fuck...

Most nowadays are designed to go unnoticed so they can survive on the system longer and extract more information.