Windows 7 worked on Windows 7. These were broadly divided into "core operating system" and "Windows client experience", in turn organized into 25 teams of around 40 developers on average. In October 2008, it was announced that Windows 7 would also be the official name of the operating system. There has been some confusion over naming the product Windows 7, while versioning it as 6.1 to indicate its similar build to Vista and increase compatibility with applications that only check major version numbers, similar to Windows 2000 and Windows XP both having 5.x version numbers. The first external release to select Microsoft
Windows Vista editions a full installation of Windows Vista through Upgrade media by bypassing the prompt to enter a license during setup, and then, once installed, reinstall the operating system over the previous installation—this essentially allows users who purchased the Upgrade version to perform a full retail installation. While the workaround is indeed possible, Microsoft has cautioned that users who perform a full installation of the operating system through this method without a genuine license for a previous version would be in violation of the Windows Vista end-user license agreement. Users can upgrade from Windows XP to Windows Vista, or upgrade from one