Boston Celtics advanced to the second stage of the NBA playoffs with a 99-65 victory over the Atlanta Hawks today.The win in Boston sealed a 4-3 series success for the Celtics and averted what was shaping up as a major shock in the Eastern Conference. The eighth-ranked Hawks were not expected to win a game in the seven-match series against the top-rated Celtics but shocked the Celtics and their fans by taking the series to the wire. In the second round, Boston will meet the Cleveland Cavaliers, who won 4-2 in their first-round series against the Washington Wizards. In the Western Conference, the Los Angeles beat the Utah Jazz 109-98 today to lead 1-0 in their second-round series.