Shares sold short in Microsoft (NASDAQ: MSFT) fell 14.1 million shares in September to 83 million. It seems that the shorts knew enough to get out ahead of good news.

So far this year, Microsoft's stock has been flat, but over the last three days it has moved up more than 3% on news that it had released its Halo 3 video game and that it is in talks to buy part of social network Facebook.

The enthusiasm about Halo may be well-placed. In the company's last fiscal year, its devices business lost $1.9 billion on $6.1 billion in revenue. The previous year was not any better. The world's largest software company needs a catalyst to drive sales of its Xbox 360, and Halo 3 may well do that.

The Facebook deal has also drawn a great deal of attention. Rival Google (NASDAQ: GOOG) is building a large advertising platform using its own search inventory combined with impressions that it gets from its AdSense network. To expand that business, it is buying DoubleClick and has a deal to sell ads on social network leader MySpace. AOL is making moves in the same business. It owns Advertising.com, the largest ad network, and has just bought behavior targeting company Tacoda.

That leaves Microsoft sitting well behind its rivals. A deal with Facebook could help expand a network around its portal, MSN. Online services lost $732 million last year.

It may be that the company is facing up to its online and devices problems. That could be good news.

Douglas A. McIntyre is a partner at 24/7 Wall St.