Shutdown/Restart Explorer Programatically on WinXP and do NOT rerun startup group

I am attempting to restart the Windows Shell Explorer programmatically.  Microsoft’s answer in Q137572 was written for Windows 95 appears incomplete for WinXP.  The knowledge base article says to send a WM_QUIT message to progman then restart explorer.exe.

If I expand this to both progman and Shell_TrayWnd (https://www.experts-exchange.com/questions/10507038/stop-explorer-cleanly.html), I get pretty close.  The one problem is that when I restart explorer.exe, programs in the startup menu always re-run.  I refer to this as my-shutdown.

If I shutdown explorer the safe interactive way (by selecting “Start/Turn Off Computer” and holding down CTRL-ALT-DEL simultaneously while pressing “Cancel”) it shuts down in what looks almost identical to my-shutdown, however when I re-start explorer now, the start menu items do not re-run themselves.  I refer to this as the clean-shutdown.

I used Spy to snoop the messages for these two windows.  Shell_TrayWnd actually received a WM_CLOSE just before the WM_QUIT, but adding this didn’t solve anything.  The Expert Exchange article actually says to use an lParam of 1 on the progman quit, but this is a mistake.  WM_QUIT only takes a wParam, and Spy shows that it is not sent on the clean-shutdown.

I used ntregmon from SysInternals to snoop the registry.  There are several differences, but I couldn’t detect anything specific to use.

To avoid the obvious question, why am I doing this, let me answer.  I am attempting to auto-install a software update over the web, and I can’t install the new DLL because the DLL provides some COM services to the shell, in this case a context-menu-handler.  At this point in the process, the silent auto-update has failed, and the user has selected that they want to install interactively and restart the shell.  I believe that this is a better solution than forcing a reboot.

Here is what I have.  I have a handle to the explorer.exe process before calling this method, so there is no need to find it.

BOOL CShell32::ShellRestart(HANDLE hProcess)
{
        if (hProcess)
        {
               // get the window handles of the program manager and system tray
               HWND hwndProgman = FindWindow("Progman", NULL);
               HWND hwndShell = FindWindow("Shell_TrayWnd", NULL);
               if (hwndProgman && hwndShell)
               {
                       // TODO: there is something else that must be done
                       // to keep explorer from running the startup group
                       // when it restarts, but I don't know what it is!!!
                       //
                       // Is it a registry setting?
 
                       // request the shell to stop
                       PostMessage(hwndProgman, WM_QUIT, 0, 0);
                       PostMessage(hwndShell, WM_QUIT, 0, 0);
 
                       // wait for these windows to shutdown
                       DWORD dwNow = GetTickCount();
                       while (TRUE)
                       {
                              _Module.YieldMessageLoop();
 
                              // wait until the system tray is running and initialized
                              if (!IsProcess(hProcess))
                              {
                                              // restart explorer
                                      STARTUPINFO si;
                                      PROCESS_INFORMATION pi;
                                      ZeroMemory(&si, sizeof si);
                                      si.cb = sizeof si;
                                      ZeroMemory(&pi, sizeof pi);
                                      if (CreateProcess(NULL, "Explorer.EXE", NULL, NULL, FALSE, 0, NULL, NULL, &si, &pi))
                                      {
                                             CloseHandle(pi.hProcess);
                                             return TRUE;
                                      }
                                      break;
                              }
 
                              // wait at most 30 seconds
                              if (GetTickCount() - dwNow > 30000)
                                      break;
                       }
               }
        }
        return FALSE;
}
 
BOOL CShell32::IsProcess(HANDLE hProcess) const
{
        DWORD dwExitCode;
        if (GetExitCodeProcess(hProcess, &dwExitCode) && dwExitCode == STILL_ACTIVE)
               return TRUE;
        return FALSE;
}