Update: Here's Why It's Windows 7
The mystery of Microsoft's Windows version count has been solved. A day after announcing (in the Windows Vista blog) that the next release of Windows will be called Windows 7, Mike Nash (Microsoft Corporate VP, Windows Product Management) added a post laying out Microsoft's Windows version numbers since Windows 3.x.
Basically, they go like this:
Version 4: Windows 95
Version 4 point releases: Windows 98, 98SE, and ME (4.0.1998, 4.10.2222 and 4.90.3000, respectively).
Version 5: Windows 2000
Version 5 point releases: Windows XP (5.1)
Version 6: Windows Vista
I was surprised to realize that Windows XP (in which Microsoft unified the code bases for Windows 9x and NT/2000) was only a point release. But at least we now know how they got to Windows 7.
By the way, for those who wanted (but were unable) to comment on my blog post yesterday, we've since transitioned to a new posting system. So feel free to try again.