Slashdot linked to this post purporting to demonstrate that it’s ridiculous to consider the next version of Windows Windows 7. They offer several lists of past releases, all of which have at least 7 elements.
Obviously, the evolution of Windows has been sufficiently tortured that reasonable people can disagree about exactly how many generations there have been. In particular, the parallel development of the 3.1/95/98/ME and NT/2000 lines makes things unusually messy. But I think it’s entirely plausible to say that there have been the following 6 generations of Windows operating systems:
1. Windows
2. Windows 2
3. Windows 3/3.1 (NT 3)
4. Windows 95/98/ME (NT4)
5. Windows XP (Windows 2000)
6. Windows Vista
Windows 98/ME were clearly incremental upgrades of Windows 95. NT3, NT4, and Win2k were business/server operating systems that were released in parallel with the consumer products. It seems pretty reasonable to say that there have been 6 major releases of Windows, and that the one they’re working on now will be the seventh.