Harding played three seasons of junior hockey in the Western Hockey League (WHL) with the Regina Pats and Brandon Wheat Kings. He won the Del Wilson and Four Broncos Memorial Trophies in 2003 as the WHL's top goaltender and most outstanding player respectively. He represented Canada at the 2004 World Junior Ice Hockey Championships, winning a silver medal. He was selected in the second round, 38th overall, of the 2002 NHL Entry Draft by the Wild. He began his professional career with the Houston Aeros of the American Hockey League (AHL), the Wild's top minor league affiliate. In the 2004–05 season, his rookie season with the Aeros, he posted a 21–16–3 record with a 2.01 goals against average (GAA).