After "Longhorn" was named Windows Vista in mid-2005, an unprecedented beta-test program was started which involved hundreds of thousands of volunteers and companies.
During this period, Microsoft was fairly quiet about what was being worked on, as their marketing and public relations focus was more strongly focused on Windows XP, and Windows Server 2003, which was released in April 2003.
Occasional builds of Longhorn were leaked onto popular file sharing networks such as IRC, Bit Torrent, e Donkey and various newsgroups, and so most of what is known about builds prior to the first sanctioned development release of Longhorn in May 2003, is derived from these builds.
Most builds of Longhorn and Vista were identified by a label that was always displayed in the bottom-right corner of the desktop.
prior to the release of Microsoft's Windows XP operating system, and continuing until November 2006.
Microsoft originally expected to ship the new version sometime late in 2003 as a minor step between Windows XP (codenamed "Whistler") and Windows 7 (codenamed "Blackcomb" and "Vienna").
Vista's original codename, "Longhorn", was an allusion to this plan: While Whistler and Blackcomb are large ski resorts in British Columbia, Longhorn is the name of a bar between the two mountains that Whistler's visitors pass to reach Blackcomb.
Gradually, Windows "Longhorn" assimilated many of the important new features and technologies slated for "Blackcomb", resulting in the release date being pushed back a few times.
Many of Microsoft's developers were also re-tasked with improving the security of Windows XP.
Faced with ongoing delays and concerns about feature creep, Microsoft announced on August 27, 2004 that it was making significant changes.
"Longhorn" development basically started afresh, building on the Windows Server 2003 codebase, and re-incorporating only the features that would be intended for an actual operating system release.
Some previously announced features, such as Win FS and NGSCB, were dropped or postponed.