C:\>start /?
Starts a separate window to run a specified program or command.
 
START ["title"] [/Dpath] [/I] [/MIN] [/MAX] [/SEPARATE | /SHARED]
      [/LOW | /NORMAL | /HIGH | /REALTIME | /ABOVENORMAL | /BELOWNORMAL]
      [/WAIT] [/B] [command/program]
      [parameters]
 
    "title"     Title to display in  window title bar.
    path        Starting directory
    B           Start application without creating a new window. The
                application has ^C handling ignored. Unless the application
                enables ^C processing, ^Break is the only way to interrupt
                the application
    I           The new environment will be the original environment passed
                to the cmd.exe and not the current environment.
    MIN         Start window minimized
    MAX         Start window maximized
    SEPARATE    Start 16-bit Windows program in separate memory space
    SHARED      Start 16-bit Windows program in shared memory space
    LOW         Start application in the IDLE priority class
    NORMAL      Start application in the NORMAL priority class
    HIGH        Start application in the HIGH priority class
    REALTIME    Start application in the REALTIME priority class
    ABOVENORMAL Start application in the ABOVENORMAL priority class
    BELOWNORMAL Start application in the BELOWNORMAL priority class
    WAIT        Start application and wait for it to terminate
    command/program
                If it is an internal cmd command or a batch file then
                the command processor is run with the /K switch to cmd.exe.
                This means that the window will remain after the command
                has been run.
 
                If it is not an internal cmd command or batch file then
                it is a program and will run as either a windowed application
                or a console application.
 
    parameters  These are the parameters passed to the command/program
 
 
If Command Extensions are enabled, external command invocation
through the command line or the START command changes as follows:
 
non-executable files may be invoked through their file association just
    by typing the name of the file as a command.  (e.g.  WORD.DOC would
    launch the application associated with the .DOC file extension).
    See the ASSOC and FTYPE commands for how to create these
    associations from within a command script.
 
When executing an application that is a 32-bit GUI application, CMD.EXE
    does not wait for the application to terminate before returning to
    the command prompt.  This new behavior does NOT occur if executing
    within a command script.
 
When executing a command line whose first token is the string "CMD "
    without an extension or path qualifier, then "CMD" is replaced with
    the value of the COMSPEC variable.  This prevents picking up CMD.EXE
    from the current directory.
 
When executing a command line whose first token does NOT contain an
    extension, then CMD.EXE uses the value of the PATHEXT
    environment variable to determine which extensions to look for
    and in what order.  The default value for the PATHEXT variable
    is:
 
        .COM;.EXE;.BAT;.CMD
 
    Notice the syntax is the same as the PATH variable, with
    semicolons separating the different elements.
 
When searching for an executable, if there is no match on any extension,
then looks to see if the name matches a directory name.  If it does, the
START command launches the Explorer on that path.  If done from the
command line, it is the equivalent to doing a CD /D to that path.