var
  bmp: TBitmap;
  DC: HDC;
begin
  bmp:=TBitmap.Create;
  bmp.Height:=Screen.Height;
  bmp.Width:=Screen.Width;
  DC:=GetDC(0);  //Дескpиптоp экpана
  bitblt(bmp.Canvas.Handle, 0, 0, Screen.Width, Screen.Height,
    DC, 0, 0, SRCCOPY);
  bmp.SaveToFile('Screen.bmp');
  ReleaseDC(0, DC);
end;

Var
  Desktop: TCanvas ;
  BitMap: TBitMap;
begin
  DesktopCanvas:=TCanvas.Create;
  DesktopCanvas.Handle:=GetDC(Hwnd_Desktop);
  BitMap := TBitMap.Create;
  BitMap.Width := Screen.Width;
  BitMap.Height:=Screen.Height;
  Bitmap.Canvas.CopyRect(Bitmap.Canvas.ClipRect,
  DesktopCanvas, DesktopCanvas.ClipRect);
  ........
end;