Hoax Viruses
Hoax viruses are designed to disrupt people by causing anxiety and panic. An emotive email warns you that a terrible virus attack is imminent, recommending that you take some inconvenient action and warn all your friends.
There is no such virus, but the message spreads quickly, mail systems slow down, helpdesks are inundated etc. When people realise that this was a hoax, there is a risk that they become wary of legitimate virus warnings.
Do not spread virus warnings. If you are worried, consult the list of hoax viruses at McAfee.
There is a less dangerous but equally annoying type of email message: the chain letter. Whether it is an ancient good luck charm, a definition of friendship, or a charity appeal - if an email message asks you to forward it to everyone that you know, then it is simply a chain letter and you should ignore it.