I think this surprising chart says it all:
What drives Microsoft is Windows and Office. Still.
I am surprised by a few things on this chart. First, I thought Office was the real cash cow at Microsoft, but it looks like Office is returning less these days. I also was surprised by the spike in Profit from Windows, but this is likely to do with Windows 7 sales likely shooting up. Finally, I am surprised at just how little Entertainment and Devices add to the bottom line. I guess XBOX is not that profitable. (Never mind Zunes!)
You can also imagine how the profit from Office and Windows allows Microsoft to continue to explore such services as Bing. While Bing may not be profitable, it may be increasingly bringing in revenue. That might be enough for now.
While this increase in profit, I guess Ballmer is safe for now.