** FILE ** Australian William Kirby, Michael Klim, Ian Thorpe, and Todd Pearson, left to right, celebrate their world record gold medal win in the 4x200m freestyle relay at the Olympic Games in Sydney, Australia, in this September 19, 2000, file photo. Five-time Olympic champion Ian Thorpe has quit competitive swimming at the age of 24. "As of 2.53 on Sunday afternoon I decided I would not be swimming the world championships," Thorpe told a news conference Tuesday November 21, 2006. (AP Photo/Tom Hanson, FILE)