I hope you're not one of the many people who has experienced receiving a piece of junk email from (gulp!) yourself.
The good news is that it's probably not your fault. The bad news is someone you know probably has an infected computer.
Many computer viruses going around multiply themselves by grabbing a person's address book and sending emails out to many of the addresses.
If you think you or someone you know might have a virus, I urge you to visit Symantec's Security Response page to see if you can figure out what you have, and how to get rid of it. Also, it's a good idea to run anti-virus software so you can be absolutely sure you DON'T get a virus!