You probably don't have a virus, if your e-mail adress has ever been posted anywhere on the internet it's open for abuse by spoofers. You can try an online scan using Kaspersky, I just did and found 2 viruses that where not found by my existing AV software. I ended up trashing my existing AV software and installing Kaspersky to get rid of the viruses (total of 36 hours of work.)