Windows Vista build 5221 (vbl ux dev checkin gamesux)

Windows Vista build 5221 (vbl_ux_dev_checkin_gamesux) is a pre-Beta 2 build of Windows Vista. This build was used as concept art in one of Microsoft's presentations, and was also shown off in several Parental Controls demonstrations at PDC 2005. A screenshot of this build was accidentally posted to Microsoft's website, and was subsequently archived by Polish website WinBeta.pl before it was taken down.

This is the earliest known build to include the start menu used in build 5252 onwards, alongside with the start orb and darker taskbar seen in other  builds.