WINDSOR, UNITED KINGDOM:  Camilla Parker Bowles shows off her engagement ring as she and Prince Charles arrive for a party at Windsor Castle after announcing their engagement earlier 10 February, 2005.  Britain's Prince Charles and his longtime companion Camilla Parker Bowles are to marry, his office announced Thursday, putting the official seal on a relationship that first blossomed 35 years ago.     AFP PHOTO/ARTHUR EDWARDS/WPA POOL  (Photo credit should read ARTHUR EDWARDS/AFP/Getty Images)