Some virus hoaxes are almost as bad as real viruses except that they get you to do their dirty work for them - like deleting files.
Check out Symantec's Hoax Notification Site before you follow the instructions in an email message that tells you to delete files or forward it to "everyone in your address book." There are many hoaxes described on that site.
There are many other sites that discuss hoaxes. Some of them (not sponsored by anti-virus companies) are:
Some hoaxes, such as the email chain letter that reported that Microsoft would pay a certain amount of money for each time the message was forwarded, can do as much damage as a real virus - flooding email servers, slowing them down until they crash and have to be rebuilt. Don't be an unwitting participant in such a scheme. If you suspect a message might be a hoax, check it out at one of the above sites.