I’ve never met a computer that wasn’t infected, even Apple computers carry viruses. This doesn’t mean that all computers are infected but what this does tell me is that many people can’t tell if their computer is infected, don’t know how or simply can’t afford to fix the problem.
If you have an infection and you tell someone to check out your latest uploads to MySpace or Facebook then you run the risk of infecting your friend’s computer. Your address book can also be stolen and your friends could start to get more spam. The longer you do nothing or what amounts to nothing to clean your computer the more the infection spreads. Your computer will become slow and non responsive until it doesn’t boot anymore. You can become the victim of Identity theft or key-loggers, the process of monitoring your key strokes and stealing your logon information etc.
Clean machines need to get monthly Windows updates, daily Virus, Spyware/Malware updates and need to be scanned on a regular basis. Changing surfing habits and avoiding dubious download habits will also go along way in keeping your computer safe and running fast.