Microsoft said users of its Windows Millennium Edition (Me) operating system risk having their files deleted by an attacker because of what it called a critical security vulnerability. It issued a patch for the flaw Wednesday.Microsoft\u00a0said users of its Windows Millennium Edition (Me) operating system risk having their files deleted by an attacker because of what it called a critical security vulnerability. It issued a patch for the flaw Wednesday.It has issued a patch for the Windows Me Help and Support Center where the URL handler for the "hcp:\/\/" prefix, used to access the center, contains an unchecked buffer.An attacker could create a URL that executes his or her code on the user's computer and gives access to local files, which can then be added to, deleted or modified. The false url could be placed on a Web page or e-mailed to the intended victim, Microsoft said.The severity of e-mail attacks would depend on the e-mail client being used. Outlook Express 6.0 or Outlook 2002 in the user's default configurations, or Outlook 98 or 2000 in conjunction with the Outlook Mail Security Update, would stop automated attacks, but the user is still vulnerable if they click on the link in an e-mail. If the user had another e-mail client, the attack could be triggered automatically, Microsoft said.For attackers to be successful they would have to lure users to their own Web site or send them an HTML e-mail. If the user is running Internet Explorer 6.0 Service Pack 1, the Help and Support Center function cannot be started automatically in Outlook Express or Outlook, Microsoft said.