Windows 10 build 10240 (winmain prs)

Windows 10 build 10240 (winmain_prs) is an unconfirmed build of Windows 10. Screenshots of the  dialog and Windows Preinstallation Environment have been shown. Unlike build 10176, it has a timebomb, and reuses the Windows branding from builds 9821 to 10166 instead of the Windows 10 one.

This is the last known build to use  branches, and also this is last known build to use old branch system.