Re: Am I good with Avast Free antivirus edition?
Microsoft Security Essentials is what you should be running if you're looking for free. The best part of it is that it will update with Windows Automatic Updates as long as you have those configured. No user intervention required.
If you're going to pay, go with NOD32 or Kaspersky. I run Symantec only on my servers - and only because it has a decent track record in that environment. Then again, I'm not web browsing in IE6 on them either. For a tech savvy person, MSE is more than adequate. If you downloading PRAWNS and other crap, you might want to look into NOD32 because it will actually monitor your browser and prevent crap from ever being downloaded. Not as seamlessly integrated as MSE, but it might be good for your dad.
If you want your PC to be safe, run online with a browser like Firefox and plugins like NoScript/Flashblock/Adblock+.