How can I tell if I have a virus?
There are many side effects of viruses but the 'best' ones will have no side effects. If you're computer is suddenly running very slowly when it was fine before could indicate malicious activity in the background. You may notice that your browser loads up with new toolbars along the top or forces you to use a specific search function other than Google. When things don't seem to be doing what they should be could also be an indicator of a virus affecting your computer security.