Windows Vista build 5421

Windows Vista build 5421 is a pre-RC1 build of Windows Vista. Screenshots of this build were shown in a MSDN blog called "User Account Control Prompts on the Secure Desktop". This build demonstrated the User Account Control and its effects on the user. Apparently, the blog replaced the images of the build with ones from build 5381, however Polish website WinBeta.pl archived the images before it got replaced.