Computer problems

Ok, yesterday I made a stupid mistake. Being in IT I should have known better. In the middle of my day, I get an email from our email server saying that it has detected a virus on my computer and in order to remove it I needed to update my virus protection. We'll almost immediately after clicking the attached zip file, I knew I had unleashed a virus on my box. My virus protection software starting going bezerk; throwing up messages about infected email messages. Ahhhgg, how could I have fallen for the oldest trick in the book?