Microsoft corporate vice president Mike Nash announced Tuesday in this entry in the Windows Vista Blog that the new version of Windows would be called Windows 7—but that its version number will be 6.1.

Nash said,

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. The only thing to read into the code versioning is that we are absolutely committed to making sure application compatibility is optimized for our customers.

This falls right in line with Microsoft’s policy of calling Windows 7 a major release while at the same time denying any changes that are likely to be generally considered major. As Paul Thurrott has noted in pieces such as this one, Microsoft’s stated plans for Windows 7 don’t seem all that major.

Microsoft certainly has reason to want Windows 7 to be seen as a major release. Vista has a pretty bad reputation, whether it’s deserved or not. If Windows 7 is perceived as nothing more than Vista SP3 or Vista R2, it could inherit Vista’s reputation.

So what have version numbers meant in the past? Microsoft’s non-NT OSs went from being known by version numbers to Windows 95, which had an internal version of 4.0. Windows 98 was 4.1 and Me was 4.9. On the NT side, Windows 2000 was version 5.0. Windows XP was version 5.1. Server 2003 was 5.2 and Windows Vista and Server 2008 are both version 6.0.

Windows saw hefty changes from 95 to Me, but those all fit under the same version number, so maybe Windows 7 can be a major release and still be 6.1. I need to see some major announcements about technological or UI changes in Windows 7 before I believe it, though.

Major release or not, nearly everyone can agree it’s confusing that Windows 7 is neither the seventh release of Windows nor version 7 of Windows. Unless, of course, you count like Nash does in that entry.