WSJ.com - Battling Google, Microsoft Changes How It Builds Software

The news got even worse: Longhorn was irredeemable because Microsoft engineers were building it just as they had always built software. Throughout its history, Microsoft had let thousands of programmers each produce their own piece of computer code, then stitched it together into one sprawling program. Now, Mr. Allchin argued, the jig was up. Microsoft needed to start over.