I won't get into the argument about which virus scanning product is the best. Warning Recently a few new threats in the form of Trojans have come on the horizon. A friend sends you a game over ICQ or you download it. This is not a virus, just a secret program hidden in the other program. Once installed it will allow a hacker with the right tools to have total access to your computer.
Many hackers get free Internet by stealing peoples accounts.
Don't accept programs sent to you even by good friends. Get a good virus scanner and keep it up to date. Many of these companies will allow you a FREE evaluation download. In some cases, you many use an evaluation copy indefinitely. They give you a 30 day demo that will fix you up.