They won it in 2008.
the Boston Celtics
As of the start of the 2007-2008 season, the Dallas Mavericks have never won an NBA championship.
The Philadelphia 76ers won the NBA Championship in 1983.
No, they have never won an NBA Championship
Kevin Garnett won the 2008 NBA championship. He won it with the Boston Celtics, after defeating the Los Angeles Lakers 4 games to 2, in the NBA Finals.
The Los Angeles Lakers won the 2008 - 2009 NBA Championship. They were competing against Dwight Howard and the Orlando Magic. Kobe Bryant was named Finals MVP.
The Boston Celtics won the NBA Championship for the 2007-08 season, after defeating the Los-Angeles Lakers in the NBA Finals. The Celtics won the series 4 games to 2.
The Los Angeles Lakers won the 2010 NBA Championship.