Launching and Closing Windows Explorer

I want to launch and close Windows Explorer from a Delphi 3 program.  Launching is no problem.  But I have tried several different methods of closing Explorer once it has been launched.  None of them work, though some of them did work when I used a Delphi test application instead of Explorer.

The following are the relevant bits of a test program I wrote to demonstrate the techniques I have tried.  The program has a single form with an edit box in which the command line is to be entered, a launch button, and a different close button for each of the closing techniques I tried.  The comment at the top of the OnClick method for each close button shows the results I got for the technique executed.

Any suggestions, please?

private
ProcessInformation : TProcessInformation;

procedure TForm1.LaunchButtonClick(Sender: TObject);
var
StartupInfo : TStartupInfo;
begin
GetStartupInfo(StartupInfo);
StartupInfo.wShowWindow := SW_SHOWNORMAL;
if CreateProcess(
    Nil,   {ApplicationName}
    PChar(CommandEdit.Text),   { lpCommandLine }
    Nil,  {lpProcessAttributes}
    Nil,  {lpThreadAttribute}
    False,  {bInheritedHandles}
    NORMAL_PRIORITY_CLASS,  {dwCreationFlags}
    Nil,  {lpEnvironment}
    Nil,  {lpCurrentDirectory}
    StartupInfo, {lpStartupInfo}
    ProcessInformation  {lpProcessInformation}
    )
then begin
  ResultLabel.Caption := 'Launched ' + CommandEdit.Text;
end else begin
  ResultLabel.Caption := 'Failed to launch ' + CommandEdit.Text;
end;
end;

procedure TForm1.Close1ButtonClick(Sender: TObject);
{This fails and returns false for Explorer.
It returns true but fails to work for the test application.}
begin
if PostThreadMessage(ProcessInformation.dwThreadId,
                     WM_CLOSE, 0, 0) then begin
      ResultLabel.Caption := CommandEdit.Text + ' closed';
end else begin
      ResultLabel.Caption := 'Failed to close ' + CommandEdit.Text;
end;
end;

procedure TForm1.Close2ButtonClick(Sender: TObject);
{This returns true but fails to work for Explorer.
It works and returns true for the test application.}
var
BrowserHandle : THandle;
begin
BrowserHandle :=
  OpenProcess(PROCESS_ALL_ACCESS, False, ProcessInformation.dwProcessId);
if TerminateProcess(BrowserHandle, 0) then begin
  ResultLabel.Caption := 'Launched ' + CommandEdit.Text;
end else begin
  ResultLabel.Caption := 'Failed to launch ' + CommandEdit.Text;
end;
end;

procedure TForm1.Close3ButtonClick(Sender: TObject);
{This fails and returns false for both Explorer and the test application.}
var
BrowserHandle : THandle;
begin
BrowserHandle :=
  OpenProcess(PROCESS_ALL_ACCESS, False, ProcessInformation.dwProcessId);
if PostMessage(BrowserHandle, WM_CLOSE, 0, 0) then begin
  ResultLabel.Caption := 'Launched ' + CommandEdit.Text;
end else begin
  ResultLabel.Caption := 'Failed to launch ' + CommandEdit.Text;
end;
end;

procedure TForm1.Close4ButtonClick(Sender: TObject);
{This returns true but fails to work for Explorer.
It works and returns true for the test application.}
begin
if TerminateProcess(ProcessInformation.hProcess, 0) then begin
  ResultLabel.Caption := 'Launched ' + CommandEdit.Text;
end else begin
  ResultLabel.Caption := 'Failed to launch ' + CommandEdit.Text;
end;
end;

procedure TForm1.Close5ButtonClick(Sender: TObject);
{This fails and returns false for both Explorer and the test application.}
begin
if PostMessage(ProcessInformation.hProcess, WM_CLOSE, 0, 0) then begin
  ResultLabel.Caption := 'Launched ' + CommandEdit.Text;
end else begin
  ResultLabel.Caption := 'Failed to launch ' + CommandEdit.Text;
end;
end;