혹시 최용일님 보시면, 용서하세요.
해결이 되지 않아, 해결된 부분 빼고 자꾸 올립니다.  --;
전번 답변 정말 감사드리구요.

아래 소스와 같이 실행을 했는데,
도대체가 되질 않습니다.
한수 가르쳐 주십시요.
그대로 복사, 붙여넣기 하시면, 테스트 해 보실수 있습니다.

VK_F1도 되질 않지만,
특히, VK_F8의 경우에는,
다음의 어느 구문으로 실행시켜도 배경색은 항상 흰색입니다.
imsiHBRUSH := CreateSolidBrush(RGB(0,0,0));   // 검정색
imsiHBRUSH := CreateSolidBrush(RGB(255,0,0)); // 빨간색
imsiHBRUSH := CreateSolidBrush(RGB(0,0,255)); // 파란색

정말 모르겠군요...


//////////////////////////////////////////////////////////////////////

program Project2;
uses
Windows,Messages,SysUtils,Graphics;

{$R *.res}

var
nX,nY:Integer;
cX,cY:Integer;

function WindowProc(TheWindow:HWND;TheMessage:UINT; WParam:WPARAM; LParam: LPARAM): Longint; stdcall; export;
var
imsiHBRUSH:HBRUSH;
imsiDC:HDC;
imsips:PAINTSTRUCT;
begin

case TheMessage of

   WM_KEYDOWN
   :begin

      Case LOWORD(WParam) of
         VK_F1:begin
            nX:=100;    nY:=100;
            imsiDC:=BeginPaint(TheWindow,imsips);
            SetTextAlign(imsiDC,TA_TOP or TA_RIGHT);
            SetTextColor(imsiDC,RGB(255,255,0));
            SetBkColor(imsiDC,RGB(255,0,0));
            TextOut(imsiDC,nX,nY,PChar('이것은'),6);
            nY:=nY+20;
            TextOut(imsiDC,nX,nY,PChar('책'),2);
            nY:=nY+20;
            TextOut(imsiDC,nX,nY,PChar('입니다'),10);
            EndPaint(TheWindow,imsips);
            Exit;
         end;

         VK_F8:begin
            imsiHBRUSH := CreateSolidBrush(RGB(0,0,125));
          SetClassLong(TheWindow,GCL_HBRBACKGROUND,imsiHBRUSH);
            DeleteObject(imsiHBRUSH);
            InvalidateRect(TheWindow,nil,TRUE);
            Exit;
         end;

      end;

   end;

   WM_DESTROY
   :begin
      PostQuitMessage(0);
      Exit;
   end;

end;

Result := DefWindowProc(TheWindow, TheMessage, WParam, LParam)

end;

function RegisterClass:Boolean;
var
WindowClass:TWndClass;
begin

WindowClass.Style       := CS_HREDRAW or CS_VREDRAW;
WindowClass.lpfnWndProc := @WindowProc ;
WindowClass.cbClsExtra  := 0;
WindowClass.cbWndExtra  := 0;
WindowClass.hInstance   := hInstance;
WindowClass.hIcon       := LoadIcon(0,IDI_APPLICATION);
WindowClass.hCursor     := LoadCursor(0,IDC_CROSS);
WindowClass.hbrBackground := COLOR_WINDOW;
WindowClass.lpszMenuName := nil;
WindowClass.lpszClassName:= PChar('test');
Result := Windows.RegisterClass(WindowClass) <>0 ;

end;

var
TheMessage:TMsg;
hWindow:HWND;
begin

if not RegisterClass then
begin
   messageBox(0,'RegisterClass Failed',nil,MB_OK);
   Exit;
end;

hWindow := CreateWindow(PChar('test'),
                         PChar('test'),
                         WS_OVERLAPPEDWINDOW or WS_VISIBLE,
                         CW_USEDEFAULT,
                         CW_USEDEFAULT,
                         CW_USEDEFAULT,
                         CW_USEDEFAULT,
                         0,
                         0,
                         hInstance,
                         nil
                         );
if hWindow = 0 then
begin
   messageBox(0,'CreateWindow Failed',nil,MB_OK);
   Exit;
end;

While GetMessage(TheMessage,0,0,0) do
begin
   TranslateMessage(TheMessage);
   DispatchMessage(TheMessage);
end;

end.

//////////////////////////////////////////////////////////////////////