How can I tell if my computer has a virus?
If you can answer "yes" to any of the following questions, your computer might have a virus. Is your computer running very slowly? A common symptom of a virus is much slower than normal computer performance. However, there can be other reasons for slow performance, including a hard disk that needs defragmenting, a computer that needs more memory (RAM), or the existence of spyware or adware. For more information about spyware, see How to tell if your computer is infected with spyware.