Former chess World Champions Anatoly Karpov (L) observes his opponent Garry Kasparov at the start of their 25th anniversary match in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Garry Kasparov (R) makes a move against his opponent Anatoly Karpov at the start of their 25th anniversary match in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Anatoly Karpov (L) and Garry Kasparov play at the start of their 25th anniversary match in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Garry Kasparov looks at the board at the start of his 25th anniversary match against Anatoly Karpov (not pictured) in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Anatoly Karpov (L) makes a move against his opponent Garry Kasparov at the start of their 25th anniversary match in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Anatoly Karpov (L) and Garry Kasparov shake hands at the start of their 25th anniversary match in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Garry Kasparov looks at the board at the start of his 25th anniversary match against Anatoly Karpov (not pictured) in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Anatoly Karpov (L) observes his opponent Garry Kasparov at the start of their 25th anniversary match in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess World Champions Garry Kasparov makes a move against his opponent Anatoly Karpov at the start of their 25th anniversary match in Valencia, September 22, 2009. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess world champion Anatoly Karpov listens during a news conference in Valencia, September 21, 2009, before his 25th anniversary match against Garry Kasparov to be held Tuesday to Thursday. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess world champion Garry Kasparov smiles at a news conference in Valencia, September 21, 2009, before his 25th anniversary match with Anatoly Karpov to be held Tuesday to Thursday. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess world champion Anatoly Karpov (L) looks at his opponent Garry Kasparov (R) during a news conference in Valencia, September 21, 2009, before their 25th anniversary match to be held from Tuesday to Thursday. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess world champion Garry Kasparov smiles at a news conference in Valencia, September 21, 2009, before his 25th anniversary match with Anatoly Karpov to be held Tuesday to Thursday. REUTERS/Heino Kalis (SPAIN SPORT CHESS) 

Former chess world champions Garry Kasparov (R) and Anatoly Karpov pose with their chess figures at a news conference in Valencia, September 21, 2009, before their 25th anniversary match to be held Tuesday to Thursday. REUTERS/Heino Kalis (SPAIN SPORT CHESS IMAGES OF THE DAY) 

Former chess world champions Garry Kasparov (L) and Anatoly Karpov shake hands at a news conference in Valencia, September 21, 2009, before their 25th anniversary match to be held Tuesday to Thursday. REUTERS/Heino Kalis (SPAIN SPORT CHESS)