A virus can cause your computer to crash, delete your precious pictures and documents and even steel sensitive information such as your credit card details. This is not propaganda, but hard facts. So whatever you do, make sure you protect your computer with a quality antivirus program. An antivirus program stops and removes viruses from your computer.
They can also be used to scan external hard drives and USB memory sticks. If you do catch a virus, your anti-virus will prevent it from doing harm and remove or quarantine it. Once that is done, your antivirus effectively blocks and warns you of new virus threats automatically.