I recently ran into a really annoying problem on my Windows 8.1 64-bit PC: every time I restarted it and booted into Windows, the Windows Explorer Libraries window would pop up. It never occurred before and I could not pinpoint any particular software or update that I had installed that would cause it to start happening.
Userinit Registry Key
create a reg file explorer_fix.reg and copy this into and run it.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"Shell"="explorer.exe"