Windows 7 is not Windows 7 at all, it's actually Windows 6.1. After revealing that there is no difference between the Windows 7 codename, product number and the official brand of the next iteration of the Windows client, Microsoft indicated that things are a tad different when it comes down to the actual code of the operating system. Mike Nash, Corporate Vice President, Windows Product Management, indicated that the Windows 7 code would in fact be packed and labeled as Windows 6.1 compared to 6.0.6001 which is Windows Vista Service Pack 1.

“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,” Nash stated, revealing that this detail changes nothing about the true nature of Windows 7. “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.”

Nash explained that Windows 7 would be nothing more than the brand of the next version of Windows. The close connection between the seventh release of Windows, the codename, and the official name is however broken when it comes down to the Windows codebase. The move is necessary to support Microsoft's promise that Windows 7 will not impact hardware and software products already compatible with Windows Vista.

“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,” Nash stated.