To be totally correct, her untitled name was Diana Frances Mountbatten-Windsor. Her offical title at the time of her death was “Diana, Princess of Wales” Many people make the mistake of refering to her (Post Divorce from the Prince of Wales) as “Princess Diana” which is totally incorrect. As a result of her divorce, she lost the Style of “Her Royal Highness” as well as “Princess” but was allowed to keep the title of “Princess of Wales” as a post title. (There were many other conditions as well, such as any further children not having any claim on the Throne, ETC) Technically, there was nothing stopping her from going back to her pre-marriage title of Lady Diana but she chose not to. I presume this is not only because so many people had come to know her with “Princess of Wales” somewhere in her title, but also because the title “Princess of Wales” allowed her a little more “strength” to add behind her many quests, not the least of which was AIDS research and rallying to have every country in the world sign the “Ottawa Treaty” Just for added info to those of you who do not know; This is the reason why the flags in the U.K. were not intitally hung at half mast when Diana, Princess of Wales died. The rules for flying the Union Jack at half mast are quite specific and at that point, Diana, Princess of Wales was only a citizen like any other, and NOT a member of the Royal Family. Contrary to popular belief, Her Majesty nor any other member of the Royal Family had any problem what so ever with the flag being flown at half mast for her. It was simply an error because of Diana, Princess of Wale’s standing; She simply wasn’t on the list of people that the flag gets lowered for when they pass away. After the out cry from the public, Her Majesty was quick to correct the oversight and ORDERED the flags lowered.