Development of Windows 7

Originally, a version of Windows codenamed Blackcomb was planned as the successor to Windows XP (codename Whistler) and Windows Server 2003. 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 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 and again Windows 7 in 2007. In 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 partners came in January 2008 with Milestone 1, build 6519. At PDC 2008, Microsoft demonstrated Windows 7 with its reworked taskbar. Copies of Windows 7 build 6801 were distributed at the end of the conference; however, the demonstrated taskbar was disabled in this build.

On December 27, 2008, Windows 7 Beta was leaked onto the Internet via BitTorrent. According to a performance test by ZDNet, Windows 7 Beta beat both Windows XP and Vista in several key areas; including boot and shutdown time and working with files, such as loading documents. Other areas did not beat XP; including PC Pro benchmarks for typical office activities and video editing, which remain identical to Vista and slower than XP.On January 7, 2009, the 64-bit version of the Windows 7 Beta (build 7000) was leaked onto the web, with some torrents being infected with a trojan. At CES 2009, Microsoft CEO Steve Ballmer announced the Windows 7 Beta, build 7000, had been made available for download to MSDN and TechNet subscribers in the format of an ISO image. The Beta was to be publicly released January 9, 2009, and Microsoft initially planned for the download to be made available to 2.5 million people on this date. However, access to the downloads was delayed because of high traffic. The download limit was also extended, initially until January 24, then again to February 10. People who did not complete downloading the beta had two extra days to complete the download. After February 12, unfinished downloads became unable to complete. Users could still obtain product keys from Microsoft to activate their copies of Windows 7 Beta, which expired on August 1, 2009. The release candidate, build 7100, has been available for MSDN and TechNet subscribers and Connect Program participants since April 30 and became available to the general public on May 5, 2009. It has also been leaked onto the Internet via BitTorrent. The release candidate is available in five languages and will expire on June 1, 2010, with shutdowns every two hours starting March 1, 2010. Microsoft stated that Windows 7 would be released to the general public on October 22, 2009. Microsoft released Windows 7 to MSDN and Technet subscribers on August 6, 2009, at 10:00 a.m. PDT. Microsoft announced that Windows 7, along with Windows Server 2008 R2, was released to manufacturing on July 22, 2009. Windows 7 RTM is build 7600.16385, which was compiled on July 13, 2009, and was declared the final RTM build after passing all Microsoft's tests internally. "The launch of Windows 7 has superseded everyone’s expectations, storming ahead of Harry Potter and the Deathly Hallows as the biggest-grossing pre-order product of all-time, and demand is still going strong," claimed managing director Brian McBride, Amazon UK on October 22."