Geoff Chappell - Software Analyst
To almost all users, every time they start Windows, the main sign that Windows has finished starting is the appearance of the desktop and taskbar, with its Start button and tray notification area. Though these are in no way essential to Windows as an operating system or even to the Win32 subsystem in user mode, they are the look and feel of Windows as ordinarily experienced. The program that starts all this is EXPLORER.EXE, albeit with the overwhelming bulk of the work being done in DLLs.
The Windows Vista EXPLORER can run in three distinct modes.
EXPLORER is ordinarily configured as the shell and is run automatically at startup (without command-line arguments) to set up the desktop and taskbar and thus provide what all the world takes to be the essential look-and-feel of Windows. This first instance is here called the EXPLORER shell process.
A lasting non-shell process is created only if EXPLORER either is run while not configured as the shell or is already running as the shell but is re-run with command-line arguments. Any such instance is here called an EXPLORER separate process.
When EXPLORER is already running as the shell but is re-run without command-line arguments, it runs for just long enough to do either of two things:
The choice depends on whether the “Launch folder windows in a separate process” checkbox in the Folder Options is clear or set. The default location is the current user’s personal folder.