'Warning!,' the email screams. 'There's a new virus going around, and Microsoft says it's the worst one yet!' After this amazing bit of hype, the email continues with 'Once this virus infects your system, it will delete all the files on your hard drive, reset your computer clock, and make your screen only show green and black!'
Anyone who has made it this far is then asked to 'forward this virus warning to everyone you know!' and 'Delete any emails you get with the title 'Have a nice day!'
This email has all the signs of a virus hoax.
First, viruses are not magical or all-powerful. Yes, they can damage your data. Viruses have been known to erase hard drives, delete documents, even forward classified documents to random email addresses. But, to date, only one virus (CIH, or Chernobyl) has actually been able to damage hardware. CIH found a way to overwrite the BIOS, or read-only memory
Second, viruses are identified by their programming, and not by the title of the email they're attached to. Once word got out to delete every email with that title, the virus programmer would just change the subject, and everyone would have to send out another virus warning, for a whole new virus, that looks exactly like the old one except for the subject line of the email.
Third, if Microsoft (or any other big-name company, for that matter) wanted to get the word out about a new virus, they would post it on their website, and not ask everyone to forward emails. Forwarded emails are very inefficient, because some people only check their email once a week. By the time they got the warning, the virus would have triggered and destroyed their computer!
The best advice about virus hoax warnings is 'don't pass them along.' The huge flood of useless emails do as much damage as the viruses they warn about.