먼저 함수 선언은..

private 
    { Private declarations } 
    procedure WMSysCommand(var msg: TWMSysCommand); message WM_SysCommand; 

//Form1.h 파일에서 ..

{

private 
    void __fastcall  WMSysCommand(TWMSysCommand &msg); //WM_SysCommand; 

BEGIN_MESSAGE_MAP
    VCL_MESSAGE_HANDLER(WM_SYSCOMMAND, TWMSysCommand , WMSysCommand)
END_MESSAGE_MAP(TForm)

}

그리고 수신하는 부분은..

procedure TForm1.WMSysCommand(var msg: TWMSysCommand); 
begin 
  if msg.CmdType and $FFF0 = SC_MINIMIZE then 
    hide 
  else 
    inherited; 
end; 


procedure TForm1.FormShow(Sender: TObject); 
var 
  hwndOwner: HWnd; 
begin 
  hwndOwner := GetWindow(Handle, GW_OWNER); 
  ShowWindow(hwndOwner, SW_HIDE); 
  // For Windows 2000, additionally call the ShowWindowAsync function: 
  ShowWindowAsync(hwndOwner, SW_HIDE); 
  ShowWindowAsync(Self.Handle, SW_HIDE); 
end; 

//다음과 같이...
void __fastcall TForm1::WMSysCommand(TWMSysCommand &msg) 
{
    if( msg.CmdType &&  $FFF0 == SC_MINIMIZE )
    {
          this->Hide();
    }
    else
       TCustomForm::Dispatch(&msg);

}

void __fastcall TForm1::FormShow(TObject *Sender); 
{
     HWND  hwndOwner;
    hwndOwner = GetWindow(Handle, GW_OWNER); 
    ShowWindow(hwndOwner, SW_HIDE); 
    // For Windows 2000, additionally call the ShowWindowAsync function: 
    ShowWindowAsync(hwndOwner, SW_HIDE); 
    ShowWindowAsync(Handle, SW_HIDE); 
}

대충 위와같을듯 하네요...

그럼..


제이원 님이 쓰신 글 :
: private
:     { Private declarations }
:     procedure WMSysCommand(var msg: TWMSysCommand); message WM_SysCommand;
:
:
: procedure TForm1.WMSysCommand(var msg: TWMSysCommand);
: begin
:   if msg.CmdType and $FFF0 = SC_MINIMIZE then
:     hide
:   else
:     inherited;
: end;
:
:
: procedure TForm1.FormShow(Sender: TObject);
: var
:   hwndOwner: HWnd;
: begin
:   hwndOwner := GetWindow(Handle, GW_OWNER);
:   ShowWindow(hwndOwner, SW_HIDE);
:   // For Windows 2000, additionally call the ShowWindowAsync function:
:   ShowWindowAsync(hwndOwner, SW_HIDE);
:   ShowWindowAsync(Self.Handle, SW_HIDE);
: end;