The five-year gap between the release of Windows XP and last month's Vista launch is not a scenario that's likely to be repeated. 

"We won't go five years, I promise, between big Windows releases," Microsoft CEO Steve Ballmer told analysts in a briefing last week.
Ballmer was talking about different kinds of innovation, and categorised Windows Vista and Office 2007 as the "broad form" of innovation, and will result in low-key operating system progress.