Tooltip of UI plug-in on Win2K

Hello!

I implemented UI plug-in DLL with Tooltip feature.
This DLL can work on the WinXP or higher OSs correctly.
But, in case of Win2K, this DLL can not show any tooltip windows.

I used sample code(refer to below) on MSDN for adding tooltip feature.

Please give me an answer.

Thanks,
Junyoung Choi
////////////////////////////////////////////////////////////////////////
void CreateMyTooltip (HWND hwnd, HWND hctrl)
{

// struct specifying control classes to register
INITCOMMONCONTROLSEX iccex;
HWND hwndTT; // handle to the ToolTip control
// struct specifying info about tool in ToolTip control
TOOLINFO ti;
unsigned int uid = 0; // for ti initialization
TCHAR strTT[30] = _T("This is your ToolTip string.");
LPTSTR lptstr = strTT;
RECT rect; // for client area coordinates

// INITIALIZE COMMON CONTROLS
iccex.dwICC = ICC_WIN95_CLASSES;
iccex.dwSize = sizeof(INITCOMMONCONTROLSEX);
InitCommonControlsEx(&iccex);

// CREATE A TOOLTIP WINDOW
hwndTT = CreateWindowEx(WS_EX_TOPMOST,
TOOLTIPS_CLASS,
NULL,
WS_POPUP | TTS_NOPREFIX | TTS_ALWAYSTIP,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
hwnd,
NULL,
ghInstance,
NULL
);

SetWindowPos(hwndTT,
HWND_TOPMOST,
0,
0,
0,
0,
SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);

/* INITIALIZE MEMBERS OF THE TOOLINFO STRUCTURE */
ti.cbSize = sizeof(TOOLINFO);
ti.uFlags = TTF_SUBCLASS;
ti.hwnd = hctrl;
ti.hinst = ghInstance;
ti.uId = uid;
ti.lpszText = lptstr;
/* GET COORDINATES OF THE MAIN CLIENT AREA */
GetClientRect (hctrl, &rect);

ti.rect.left = rect.left;
ti.rect.top = rect.top;
ti.rect.right = rect.right;
ti.rect.bottom = rect.bottom;


VERBOSE(DLLTEXT("Tooltip : %d, %d, %d, %d \r\n"), ti.rect.left,
ti.rect.top, ti.rect.right, ti.rect.bottom);

/* SEND AN ADDTOOL MESSAGE TO THE TOOLTIP CONTROL WINDOW */
SendMessage(hwndTT, TTM_ADDTOOL, 0, (LPARAM) (LPTOOLINFO) &ti);
}