Late edition: I quote MS - To upgrade to Windows XP Tablet PC Edition 2005 from older Tablet PC versions, you must download the Windows XP Service Pack 2 (SP2). SP2 includes all of the new Tablet PC functionality as well as better protection against hackers, viruses, and worms. Please note that downloading SP2 will not make a traditional PC into a Tablet PC. Learn more about what defines a Tablet PC.