Originally, a version of Windows codenamed Blackcomb was planned as the successor to Windows XP and Windows Server 2003 in 2000. Major features were planned for Blackcomb, including an emphasis on searching and querying data and an advanced storage system named WinFS to enable such scenarios. However, an interim, minor release, codenamed "Longhorn," was announced for 2003, delaying the development of Blackcomb. By the middle of 2003, however, Longhorn had acquired some of the features originally intended for Blackcomb. After three major viruses, the Blaster, Sober, and Sobig worms, exploited flaws in Windows operating systems within a short time period in 2003, Microsoft changed its development priorities, putting some of Longhorn's major development work on hold while developing new service packs for Windows XP and Windows Server 2003. Development of Longhorn (Windows Vista) was also restarted, and thus delayed, in August 2004. A number of features were cut from Longhorn. Blackcomb was renamed Vienna in early 2006.
When released, Windows Vista was criticized for its long development time
, performance issues, its spotty compatibility with existing hardware and software on launch, changes affecting the compatibility of certain PC games, and unclear assurances by Microsoft that certain computers shipping with XP prior to launch would be "Vista Capable" (which led to a class action lawsuit), among other critiques. As such, adoption of Vista in comparison to XP remained somewhat low.
In July 2007, six months following the public release of Vista, it was reported that the next version of Windows would now be codenamed Windows 7, with plans for a final release within three years.
Bill Gates, in an interview with
Newsweek, suggested that Windows 7 would be more "user-centric".
 Gates later said that Windows 7 would also focus on performance improvements.
Steven Sinofsky later expanded on this point, explaining in the
Engineering Windows 7 blog that the company was using a variety of new tracing tools to measure the performance of many areas of the operating system on an ongoing basis, to help locate inefficient code paths and to help prevent performance regressions.
Senior Vice President Bill Veghte stated that
Windows Vista users migrating to Windows 7 would not find the kind of device compatibility issues they encountered migrating from
 An estimated 1000 developers 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