Viruses come in many shapes and sizes, and can be difficult to combat. We recommend Avast, it is a lightweight and simple program to use. Although no anti-virus program will be perfect, although Avast is a good front line defence.
The best protection against any virus is to backup your files, all of them. Ideally, you would want to have 3 copies of the your files: on your system, on a local external hard drive, and on an offsite backup location.
Be extremely careful where you click. Microsoft says 44.8 percent of Windows virus infections happen because the computer user clicked on something.