They lined up at midnight by the thousands and attended party launches across the country. But they weren't dressed up like Harry Potter. They were fans of Halo 3, the third installment of the Halo video game series starring Master Chief. Microsoft Corp. announced today that the hot game raked in sales of $170 million on its first day--about $50 million more than its predecessor in 2004. Microsoft is counting on the success of Halo 3, the final chapter in the trilogy, to ramp up the company's declining entertainment unit. But experts aren't so sure this one event will save Microsoft in the long run. "This is an event thing around Halo 3 and that will eventually run out, while the Wii continues as an ongoing engaging platform," said Rob Enderle of Enderle Associates.