Essential freeware for newbie pc users?

[Rare]

My brother and his wife recently bought a new very basic desktop pc. This is the first they've ever owned and the only computer experience they've ever had was with our mother's pc which was filled to the brim with viruses; she's a clicker.

I tried to tell them about only opening email from trusted sources and not downloading files indiscriminately but the truth is I can almost guarantee they are going to get viruses(or other problems) on their pc without me to stand over their shoulders and police their surfing/downloading habits.

Is there any essential freeware for Windows machines out there where I can significantly reduce the number of viruses they're going to fill their pc up with(besides a good anti-virus program). I know Firefox has some great security add-ons but at the same time I don't want to totally restrict their surfing/computer experience, (I just don't want to see them disappointed with another messed up computer.)

These programs, ideally, should be the out-of-sight-out-of-mind variety; I think anything that requires a lot of maintenance would be more than they could handle.

thanks for any suggestions!

 

[Aland]

PC World, a trusted technology review magazine, recently ranked the best free antivirus applications.
Avira AntiVir Personal was ranked 1st. It offers the best detection and malware (virus, spyware, etc.) elimination rate. It also has a quite well polished interface, although sometimes it is better suited for advanced users. In addition, you have to put up with pop-up ads.
Alwil Avast Antivirus Home Edition, ranked 2nd. It offers good protection. It is okay, not so good on the interface part.
AVG 8.5 free ranked third. It has a very good, simple interface. However, it's not so good at detection rates, compared to the better ones (a detection rate of 95.8%, not too bad!).
Microsoft Security Essentials ranked fourth. I heard it is quite good.
I am not so sure, but Panda Cloud Antivirus could be out of beta (testing mode). It is made by a very good antivirus company and offers very promising detection and elimination rates when PC World tested it as a beta. If it is now out, give it a try if you want.

Hope you find your perfect antivirus software.