Although having a virus on a computer doesn't necessarily mean that a computer will be irreparably harmed, it's important to consider immediate virus removal if you discover that your machine has been infected because some viruses can actually impact the integrity of the hardware in a machine. A virus will usually first cause some sort of issue with the software of the computer but the really virulent infections may travel to the hardware of the machine and cause it to stop working. Having a virus scanner will reduce the likelihood that a virus will overtake the computer without an owner knowing.