Re your dad getting infected "all the time," there are typically a handful of ways to get infected:
1) Being connected to the Web with the firewall turned off (you'll be infected to the gills in a matter of minutes)
2) Opening infected e-mail attachments
3) Being tricked, by phishing e-mails, into going to a Website that is infected. From what I've read, this is now the fave tactic of cyber crooks. People are gullible, and they know that.
4) Visiting infected Websites that are intentionally or unintentionally serving up malware (some are designed to do it, while others are legitimate sites that have been hacked). X-rated sites and file sharing sites are notorious for serving up malware, particularly spyware.
5) Being tricked by fake pop-up ads that claim your PC is infected and you need to "click here to remove" the virus or whatever. Others claim your PC is "running slow" and suggest you "click here to optimize system speed" or use similar verbiage. They are themselves malware.
6) Plugging in an infected flash drive or floppy disk
Use mechbgon's excellent guide for PC security and you should reduce the attack surface to almost zero. I'll just add that Spyware Doctor outperforms SuperAntiSpyware and all other anti-spyware apps in terms of both detection and removal capabilities. Webroot's Spy Sweeper is a close second. I've used SD for several years now and it often detects malware that other a-v scanners miss entirely. You can actually use it in tandem with a good a-v as long as you turn off its real-time monitoring (or turn off the a-v's real-time monitoring). Also, 64-bit versions of Windows are the most secure because they are ostensibly immune to rootkits, arguably the worst kind of malware (and certainly the hardest to detect and remove).
Ditch AVG. It is not as good at proactive detection as some of the top tier apps like NOD32, MSE, Avira, BitDefender and eScan. Norton sucks at proactive detection, and McAfee is even worse.
Know that once you're infected, it's too late. Nine times outta ten you have to reformat and re-install Windows because most malware nowadays corrupts the registry to the hilt and often overwrites Windows' .dll (dynamic link library) files too. Undoing those things can sometimes be done manually, but results aren't guaranteed.
And like mechbgon says, Acronis True Image is a great idea. He turned me on to it a few years ago and I've had great success with it too. At ~$35-40 it's really cheap insurance.