Computer viruses are a problem that we all face particularly as they can be easily spread via email over the internet. Running good antivirus software (and keeping its signature file up to date) is essential to help stop viruses from getting into your computer system.
In addition to actual viruses emails can contain warnings about viruses. Some of these warnings that you receive are genuine and others are hoaxes. If you apply the suggested fixes presented to you in a hoax email you can cause problems for yourself rather than fixing them.