Once again, an advertisement for your friendly neighborhood virus scanning software ... whatever it may be. The two biggest companies -- Norton AntiVirus (Symantec) and McAfee -- have good website pages about viruses ... and about hoaxes.
BEFORE you send out that warning to everyone you know that XYZ file will destroy their computer, check it out. When you receive a warning from someone else, check it out yourself, and when it turns out to be a bogus warning (as it almost invariably will), invite your "friend" who warned you to check it out before too.
Be polite, but be firm. If someone sends you a second or third "warning" that turns out upon checking to be bogus, cut them off (and tell them you are doing so and why).
(And then be nice about "not" cutting them off, when they apologize and promise to do better, of course)
But try to teach everyone you know: CHECK OUT "VIRUS" WARNINGS _BEFORE_ YOU PASS THEM ON!!!!!!!
P.S. Long time no see, everyone.