If you receive an email from Microsoft®, McAfee®, Symantec or any other software companies that attaches a program saying it is an update, patch or fix for a virus... DISCARD the note without opening. Never, ever open the attached file.
Most (if not all) software companies will never send you a note with a file attached. If they do an update or patch a critical flaw they might send you an email without any attachments! Be paranoid and don't use the provided link. Go to your browser and type in the link yourself (if you don't have the link already bookmarked). The reason is that some trojans/viruses take advantage of a flaw in how some browsers render web pages (if you have not applied the patch) and you won't be sent to the site that is in the email.