製品名の中の 7 は、Windows 1.0 / Windows 2.0 / Windows 3.x（および Windows NT 3.1）/ 4.x（Windows 95、Windows 98、Windows 98 Second Edition、Windows Me、およびWindows NT 4.0）/ 5.x (Windows 2000,Windows XP) / 6.0 (Windows Vista) に続く7番目のクライアント向けのメジャー リリースであることに由来している。 (参照)
Anyway, the numbering we used is quite simple. The very first release of Windows was Windows 1.0, the second was Windows 2.0, the third Windows 3.0.
Here's where things get a little more complicated. Following Windows 3.0 was Windows NT which was code versioned as Windows 3.1. Then came Windows 95, which was code versioned as Windows 4.0. Then, Windows 98, 98 SE and Windows Millennium each shipped as 4.0.1998, 4.10.2222, and 4.90.3000, respectively. So we're counting all 9x versions as being 4.0.
Windows 2000 code was 5.0 and then we shipped Windows XP as 5.1, even though it was a major release we didn't' want to change code version numbers to maximize application compatibility.
That brings us to Windows Vista, which is 6.0. So we see Windows 7 as our next logical significant release and 7th in the family of Windows releases. (参照)
OS名：Microsoft Windows 7 Home Premium バージョン：6.1.7601 Service Pack 1 ビルド 7601