The first Tuesday of each month is Microsofts Patch Tuesday, when the company releases security patches and upgrades for its software and operating systems. But today (Apr. 8) is a Patch Tuesday among Patch Tuesdays: its the last time Microsoft will release updates for the aged, but still widely used, Windows XP operating system, as well as Microsoft Office 2003 and Internet Explorer 6. Some security experts call today the XPocalypse and warn that XP operating systems will soon be hit with a barrage of attacks and exploits.