Windows Longhorn build 3663

Windows "Longhorn" build 3663 is an unleaked build of Windows Longhorn.

It is the earliest known build for which screenshots exist, and possibly the first build based on the Windows Server 2003 Release Candidate 1 codebase. A rumor exists that the build was leaked in the far past, but due to the low interest, the download links were permanently removed. There is no evidence to support this rumor, however, and it can be safely assumed that there was never any leak beyond a few screenshots.

Visual changes in the build include replacement of the colored Windows flag on the start button with a single white color variant. It also seems to have the login screen from build 3683 and disk space indicators in Explorer. Otherwise, this build is not much different from Windows XP or Server 2003.

A fake YouTube video of this build surfaced on 18 February 2021, but then it was removed.