The 2 suggestions: 1.) Load a software firewall and AV software and
learn how to configure it.
2.) Keep it updated
OK, I admit this looks like 3 suggestions. There is a myth out in the land of computer users that hardware and software manufacturers tell you everything you need to know and that they sell you everything you need in the package with your new computer. In most cases this is not true, and leads to horrible messes. On the other side of the question, the main reason why computer sellers do not tell you everything you need to know, and sell you all the software that you need is that they either; do not know what you need, and their PC at home is loused up with spyware and viruses, or they know a lot about the subject and assume you know as much as they do about computers. They may also be apathetic and not give a flip if your PC experience is as much fun as it could be. They are also ruled by a certain ethic to sell at the lowest price possible, and so they leave out the little add-ons like yearly subscription feed for AV software, that might cause you to go next door to buy the PC.
Hardly anybody who buys cake mix doesn't already know that it will require an egg, and maybe some milk that are not included in the package, but the cashier does not ask you if you want milk and eggs to make your cake with. All the sales mentalities above could be involved in them not making that suggestion, but... when you get it home and realize you have to come back to the store and buy a couple of bucks more supplies to fix the cake, you are not going to be upset or stressed. The cake mix cost a buck. The hard costs to make your cake just tripled, but you probably will not freak out/ It is really the same with PCs. The hardware is much cheaper than the software, and nobody ever seems to tell you that you need to know how to use your firewall and AV software, except your cousin Cletus, who tells you everything wrong, says it is how he handles it, and then tells you he has to run his restore disk every 2 days.
As soon as you get a PC, load a software firewall product on it. There are several to choose from, but what I use is Zone Alarm. I use Zone Alarm because the interface is easy to configure (if you read the tutorial) and the free version is not a disabled firewall. It is quite sufficient to tell me when a program attempts to access the internet or when a machine outside attempts to access me.
When a program you are not currently active with, like betterinternet.exe, attempts to access the Internet; this is a really good sign that things are not as quiet as you think. I am not happy with the Windows Firewall that comes out with WinXP SP2, because it does too much behind the scenes, rather than telling me right out front that there is an issue. the SP2 fiewall is also not very easy to configure. How do you tell it to allow sharing across your LAN with all the machines except for the public machine that sits in the front room? or your teenager's PC. It is easy to set the Zone Alarm interface to allow some and not allow others. The WinXP SP2 firewall is better than nothing, however, if you are running XP.
I even suggest that people who are on dial-up connections use a software firewall. Did you know that you receive a ping from an outside server more than once per hour on a dial-up connection? Some of these are the ISP's server checking to see if you are a live (not idle) node. Some of the pings are script-kiddies or worms testing IP ranges for open ports to do an exploit on. Juniper networks says an unprotected computer is compromised in 20 minutes or less after hooking up to the internet. A firewall helps to make you safer.
About antivirus software. The "pro" version of ZoneAlarm has an antivirus feature, but I am a proponent of separating the features. My logic is that you do not want all of your protection tied to the same piece of software, just in case an exploit comes along that disables that piece. There are worms that specifically attack Norton AV and rename themselves norton.exe, which means that when your PC starts up, you automatically reistall the worm, as the PC thinks you are loading your AV software. Personally, I like to use a slightly more obscure AV software, BitDefender or AVG, as (so far) there are no worms programmed to be BitDefender or AVG -killers.