Screen Saver appears black....

Why my screen saver appears black??  I try not to set the coords out of range... but I still can't get it right?? WHY?????

Below is the code...
#include <windows.h>
#include <scrnsave.h>
#include "scrsav.h"

LRESULT WINAPI ScreenSaverProc(HWND, UINT, WPARAM, LPARAM);
BOOL WINAPI ScreenSaverConfigureDialog(HWND, UINT, WPARAM, LPARAM);
BOOL WINAPI RegisterDialogClasses(HANDLE);
void vLoadStrings(VOID);
void MoveImage(HWND hWnd);

char szBMName1[]="BMImage1";
char szBMName2[]="BMImage2";
char szBMName3[]="BMImage3";
char szBMName4[]="BMImage4";
HBITMAP hBitmap1, hBitmap2;  // bitmap handles
HBITMAP hBitmap3, hBitmap4;

static int xPos;            // X position
static int yPos;            // Y position
static int xPosInit;      // init X position
static int yPosInit;      // init Y position
static int xStep;            // X step size
static int yStep;            // Y step size
static int iDelay;            // image delay
int iTimer;            // speed control for image

// main entry point for screen saver messages.
LRESULT WINAPI ScreenSaverProc(HWND hWnd, UINT messg,
                                             WPARAM wParam, LPARAM lParam){
      RECT rc;
      switch (messg)
      {
            case WM_CREATE:
                  // load screen saver strings
                  vLoadStrings();

                  // get initial settings for image
                  xPosInit = 30;
                  yPosInit = 30;
                  xStep = 2;
                  yStep = 2;
                  xPos = xPosInit;
                  yPos = yPosInit;
                  iDelay = 40;

                  // load all four bitmapped images
                  hBitmap1 = LoadBitmap(hMainInstance, szBMName1);
                  hBitmap2 = LoadBitmap(hMainInstance, szBMName2);
                  hBitmap3 = LoadBitmap(hMainInstance, szBMName3);
                  hBitmap4 = LoadBitmap(hMainInstance, szBMName4);

                  // start system timer
                  iTimer = SetTimer(hWnd, ID_TIMER, iDelay, NULL);

                  break;

            case WM_TIMER:
                  MoveImage(hWnd);
                  break;

            case WM_DESTROY:
                  // when finished, delete bitmaps
                  if(hBitmap1)
                        DeleteObject(hBitmap1);
                  if(hBitmap2)
                        DeleteObject(hBitmap2);
                  if(hBitmap3)
                        DeleteObject(hBitmap3);
                  if(hBitmap4)
                        DeleteObject(hBitmap4);

                  // destroy the system timer
                  KillTimer(hWnd, ID_TIMER);
                  sndPlaySound(NULL, 0);
                  break;

            case WM_ERASEBKGND:
                  // prepare for erasing whole screen
                  GetClientRect(hWnd, &rc);
                  FillRect((HDC)wParam, &rc, (HBRUSH) GetStockObject(BLACK_BRUSH));
                  return 0L;

            default:
                  break;
      }
      return (DefScreenSaverProc(hWnd, messg, wParam, lParam));
}
// Register the window
BOOL WINAPI RegisterDialogClasses(HANDLE hInst)
{
      return true;
}
void vLoadStrings(VOID)
{
      LoadString(hMainInstance, idsAppName, szAppName,
                        APPNAMEBUFFERLEN);
      LoadString(hMainInstance, IDS_NAME, szName, TITLEBARNAMELEN);
      LoadString(hMainInstance, idsScreenSaver, szScreenSaver, 22);
      LoadString(hMainInstance, IDS_DESCRIPTION, "TesT", 4);
}
// Screen Saver interface
BOOL WINAPI ScreenSaverConfigureDialog(HWND hDlg,
                                                         UINT messg,
                                                         WPARAM wParam,
                                                         LPARAM lParam)
{
      return FALSE;
}
void MoveImage(HWND hWnd)
{
      HDC hdc, hmdc;
      BITMAP bm;
      RECT rcWnd;
      static RECT rcFill;

      GetClientRect(hWnd, &rcWnd);
      GetObject(hBitmap1, sizeof(bm), (LPSTR)&bm);

      xPos += xStep;
      yPos += yStep;

      hdc = GetDC(hWnd);
      hmdc = CreateCompatibleDC(hdc);

      // draw image 1
      SelectObject(hmdc, hBitmap1);
      GetObject(hBitmap1, sizeof(bm), (LPSTR)&bm);
      BitBlt(hdc, xPos, yPos, bm.bmWidth, bm.bmHeight,
                  hmdc, 0, 0, SRCCOPY);
      Sleep(iDelay);

      // draw image 2
      SelectObject(hmdc, hBitmap1);
      GetObject(hBitmap2, sizeof(bm), (LPSTR)&bm);
      BitBlt(hdc, xPos, yPos, bm.bmWidth, bm.bmHeight,
                  hmdc, 0, 0, SRCCOPY);
      Sleep(iDelay);

      // draw image 3
      SelectObject(hmdc, hBitmap1);
      GetObject(hBitmap3, sizeof(bm), (LPSTR)&bm);
      BitBlt(hdc, xPos, yPos, bm.bmWidth, bm.bmHeight,
                  hmdc, 0, 0, SRCCOPY);
      Sleep(iDelay);

      // draw image 4
      SelectObject(hmdc, hBitmap1);
      GetObject(hBitmap4, sizeof(bm), (LPSTR)&bm);
      BitBlt(hdc, xPos, yPos, bm.bmWidth, bm.bmHeight,
                  hmdc, 0, 0, SRCCOPY);
      Sleep(iDelay);

      // examine left and right window edges
      if((xPos + bm.bmWidth > rcWnd.right) || (xPos < rcWnd.left))
            xStep =- xStep;      

      // examine top and bottom window edges
      if((yPos + bm.bmHeight > rcWnd.bottom) || (yPos < rcWnd.top))
            yStep =- yStep;      

      // do some erasing on the screen
      rcFill.left = xPos;
      rcFill.right = xPos + bm.bmWidth;
      rcFill.bottom = yPos;
      rcFill.top = yPos + bm.bmHeight;
      FillRect(hdc, &rcFill, (HBRUSH) GetStockObject(BLACK_BRUSH));
      DeleteDC(hmdc);
      ReleaseDC(hWnd, hdc);
}