Windows 10 build 10240 (winmain prs)

Windows 10 build 10240 (winmain_prs) is an unleaked build of Windows 10. Screenshots of the "About Windows" 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.