Why Windows 7 you ask?

the first release of Windows = 1.0,
.. the second was Windows 2.0,
...the third Windows 3.0.
.... NT = Windows 3.1.
..... 95 v. 4.0
...... 98, 98 SE, ME =4.0.1998, 4.10.2222, and 4.90.3000, respectively.
....... 2000 v 5.0...Windows XP v. 5.1
........ Vista v. 6.0

voila! Windows 7!

Vista Blog

Oops, make that v.6.1

"We learned a lot about using 5.1 for XP and how that helped developers with version checking for API compatibility. We also had the lesson reinforced when we applied the version number in the Windows Vista code as Windows 6.0– that changing basic version numbers can cause application compatibility issues.

So we decided to ship the Windows 7 code as Windows 6.1 - which is what you will see in the actual version of the product in cmd.exe or computer properties.

There’s been some fodder about whether using 6.1 in the code is an indicator of the relevance of Windows 7. It is not.

Windows 7 is a significant and evolutionary advancement of the client operating system. It is in every way a major effort in design, engineering and innovation. "
http://images.google.ca/imgres?imgurl=http...8UIlocXMarDOEA=

Microsoft aims Windows 7 for 2009 holiday season
http://news.cnet.com/8301-13860_3-10084486-56.html