By Peter Henderson

LOS ANGELES (Reuters) - Microsoft Corp's "Halo 3" video game set an opening-day U.S. sales record of $170 million, outdoing any video game or movie debut and giving the company's money-losing entertainment unit a strong boost toward profitability.

Alien-shooting fans also surged onto Microsoft's Xbox Live online service. More than a million members took up virtual arms in "Halo 3" in the first 20 hours on September 25, the day the game debuted, Microsoft said on Wednesday.

"Halo 3" easily surpassed its predecessor, 2004's "Halo 2," which racked up $125 million on the first day. The $60 game also beat the $59 million U.S. opening-day movie box office record, set by "Spider-Man 3."

"It's a good number," said Andy Miedler, technology analyst at Edward Jones. "This certainly goes a long way toward bringing Microsoft's entertainment division toward that full-year profitability, which we think is important for investors," he added. Microsoft aims for a profit for the division in the current fiscal year.

The game is also key to Microsoft's quest to widen its lead over rival Sony Corp in the battle for industry dominance of the current generation of game machines.

The game, in which players try to save humanity from an army of aliens, had drawn wide praise from reviewers for its lush settings, cinematic story and breadth of features.

The first two "Halo" games have sold a combined 15 million copies and cemented Microsoft as a serious player in a video game industry that was dominated by Sony's PlayStation 2.

Sony's follow-up PlayStation 3 is more expensive than the Xbox 360 and so far lacks any "system-seller" games like "Halo 3."

However, "Halo 3" is targeted firmly at the Xbox's core male audience, for whom realistic combat games are a staple. It does little to widen the machine's appeal to a more casual audience that is being courted with tremendous success by Nintendo Co Ltd's Wii console.

(Additional reporting by Daisuke Wakabayashi in Seattle)
© Copyright 2007 Reuters.