How can I tell If my computer has been infected by a virus?

The best way to tell if your system is infected is to use an anti-virus program loaded with up-to-date virus definitions. Also, take notice and pay attention to odd or unreliable behavior with your computer. This doesn’t “prove” that your computer is infected, but it does indicate something that needs attention and perhaps intervention. Often the search for an infection leads to finding corrupted or damaged files or applications, or even incipient system problems, which have nothing to do with a virus infection. You know your computer better than anyone else, and if it begins to operate in a way that seems “wrong” to you, you should start investigating.