DestroyWindow newby question.

I have a simple test program that I have been using to develop a splash screen. There are two problems with it.

1. If I do a 'DestroyWindow' for the splash screen and then try to do a 'MessageBox' then the message box is not displayed (The function returns code 0x01). Any MessageBox before the DestroyWindow call works however.

2. If the splash screen is hidden by another window it is not re-painted when it is un-hidden.

The code that demonstrates these problems is:-

#include <windows.h>

HINSTANCE    hSplashInstance;
HINSTANCE    hSplashInst;
HWND            hSplashWnd;
HBITMAP        imgHandle;
BITMAP            gBitMap;

LRESULT CALLBACK SplashProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
      PAINTSTRUCT      ps;
      HDC                  hdc;
      HDC                  hDCMem;

      switch (message) {
      case WM_PAINT:
            hdc = BeginPaint(hWnd, &ps);
            // TODO: Add any drawing code here...
            hDCMem = CreateCompatibleDC(hdc);
            SelectObject(hDCMem, imgHandle);
            SetMapMode(hDCMem, GetMapMode(hdc));  
            // Draw the bitmap using the BitBlt function        
            if (BitBlt(
                  hdc,                // The destination device context
                  0, 0,               // Coordinates of the destination rectangle
                  gBitMap.bmWidth,   // Width of the dest. and source rectangle
                  gBitMap.bmHeight,// Height of the dest. and source rectangle
                  hDCMem, 0, 0, SRCCOPY)) {
                  DeleteDC(hDCMem);
            }

            RECT rt;
            GetClientRect(hWnd, &rt);

            EndPaint(hWnd, &ps);
            break;
      case WM_DESTROY:
            PostQuitMessage(0);
            break;
      default:
            return DefWindowProc(hWnd, message, wParam, lParam);
   }
   return 0;
}


BOOL InitSplashInstance(HINSTANCE hSplashInstance, int nCmdShow) {
      //
      imgHandle = (HBITMAP)LoadImage(NULL,"splash.bmp",NULL,NULL,NULL,LR_LOADFROMFILE);
      if (!imgHandle) {
            return FALSE;
      }
      GetObject(imgHandle, sizeof(BITMAP), &gBitMap);

      hSplashInst = hSplashInstance; // Store instance handle in our global variable



      hSplashWnd = CreateWindowEx(WS_EX_CLIENTEDGE | WS_EX_DLGMODALFRAME |
       WS_EX_WINDOWEDGE, "SplashClass", NULL, WS_POPUP,
         (GetSystemMetrics(SM_CXSCREEN) - gBitMap.bmWidth) / 2,
         (GetSystemMetrics(SM_CYSCREEN) - gBitMap.bmHeight) / 2,
         gBitMap.bmWidth, gBitMap.bmHeight,
       NULL, NULL, hSplashInstance, NULL);
             
      if (!hSplashWnd) {
            return FALSE;
      }

      ShowWindow(hSplashWnd, nCmdShow);
      UpdateWindow(hSplashWnd);

      return TRUE;
}

ATOM SplashRegisterClass(HINSTANCE hSplashInstance) {
      WNDCLASSEX wcex;

      wcex.cbSize = sizeof(WNDCLASSEX);

      wcex.style = CS_HREDRAW | CS_VREDRAW;
      wcex.lpfnWndProc = (WNDPROC)SplashProc;
      wcex.cbClsExtra = 0;
      wcex.cbWndExtra = 0;
      wcex.hInstance = hSplashInstance;
      wcex.hIcon = NULL;
      wcex.hCursor = NULL;
      wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
      wcex.lpszMenuName = NULL;
      wcex.lpszClassName = "SplashClass";
      wcex.hIconSm = NULL;

      return RegisterClassEx(&wcex);
}

int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow) {
      int      retval;

      // Create and display a SPLASH SCREEN
      SplashRegisterClass(hSplashInstance);
      if(!InitSplashInstance(hSplashInstance, nCmdShow)){
            return FALSE;
      }

      Sleep(2000);

      DestroyWindow(hSplashWnd);

      retval = MessageBox(NULL, "test message", "Diagnostics", MB_APPLMODAL|MB_ICONSTOP|MB_OK);
      Sleep(2000);

      return(0);
}