Longhorn Build 3683
Leaked November 19, 2002. First public leak of Windows “Longhorn”. This build is from Lab 06; contained extras from the Avalon lab that are not seen in other builds (new display properties dialog box, etc). Some features were broken, such as Internet Explorer downloads.
File Size = 529 MB (WinBeta) (555,421,696 bytes)

Longhorn Build 4008
Leaked February 28, 2003. Second leak. Contained a cleaner version of the “Plex” visual style; Internet Explorer downloads fixed, more sidebar tiles.
File Size = 655 MB (WinBeta) (687,116,288 bytes)

Longhorn Build 4015
Leaked April 2003. Third Leak. We prefer to call this the build from hell. Not much different from 4008, except the new style taskbar was enabled by default and could only be disabled by turning off the sidebar. This build consumed HUGE amounts of memory in very little time.
File Size = 668 MB (WinBeta) (700,616,704 bytes)

Longhorn Build 4029
Leaked September 23, 2003. Fourth leak. Displayed the beginnings of the new style Explorer windows, contained a new sidebar clock.
File Size = 687 MB (Original) (721,195,008 bytes)

Longhorn Build 4051
Leaked October 25, 2003. Released at the Professional Developer Conference, this build was supposed to be quite stable, as it was the first developer preview of Longhorn, but it ended up being horrible as far as being able to develop and test sidebar tiles went. It just leaked too much memory which hindered the ability to do anything useful with it. Introduction of the “Slate” theme, “Plex” was removed.
File Size = 694 MB (WinBeta) (710,994 KB)

Longhorn Build 4053
Leaked March 1, 2004. Explorer memory leak seems to have been fixed for the most part. More responsive than 4051.
File Size = 676 MB (WinBeta) (708,943,872 bytes)

Longhorn Build 4074
Released at the WinHEC Engineering Conference on May 4, 2004. New features include the Jade theme, more sidebar tiles, etc.
File Size = 733 MB (WinBeta) (769,388,544 bytes)