To mess up your Windows box, you just need to work on it.
First, look at the two factors that cause email viruses and worms to propagate: social engineering, and poorly designed software.
Social engineering is the art of conning someone into doing something they shouldn’t do, or revealing something that should be kept secret. Virus writers use social engineering to convince people to do stupid things, like open attachments that carry viruses and worms.
Poorly designed software makes it easier for social engineering to take place, but such software can also subvert the efforts of a knowledgable, security-minded individual or organization.
Together, the two factors can turn a single virus incident into a widespread disaster.