LONG GetRegKey(HKEY key, LPCTSTR subkey, LPTSTR retdata)
{
    HKEY hkey;
    LONG retval = RegOpenKeyEx(key, subkey, 0, KEY_QUERY_VALUE, &hkey);

    if (retval == ERROR_SUCCESS) {
        long datasize = MAX_PATH;
        TCHAR data[MAX_PATH];
        RegQueryValue(hkey, NULL, data, &datasize);
        lstrcpy(retdata,data);
        RegCloseKey(hkey);
    }

    return retval;
}

void __fastcall TfrmMain::Button1Click(TObject *Sender)
{
    TCHAR key[MAX_PATH + MAX_PATH];
    char url[] = "http://www.msn.com";

    // First try ShellExecute()
    HINSTANCE result = ShellExecute(NULL, _T("open"), url, NULL,NULL, SW_SHOW);

    // If it failed, get the .htm regkey and lookup the program
    if ((UINT)result <= HINSTANCE_ERROR) {

        if (GetRegKey(HKEY_CLASSES_ROOT, _T(".htm"), key) == ERROR_SUCCESS) {
            lstrcat(key, _T("\\shell\\open\\command"));

            if (GetRegKey(HKEY_CLASSES_ROOT,key,key) == ERROR_SUCCESS) {
                TCHAR *pos;
                pos = _tcsstr(key, _T("\"%1\""));
                if (pos == NULL) {                     // No quotes found
                    pos = strstr(key, _T("%1"));       // Check for %1, without quotes 
                    if (pos == NULL)                   // No parameter at all...
                        pos = key+lstrlen(key)-1;
                    else
                        *pos = '\0';                   // Remove the parameter
                }
                else
                    *pos = '\0';                       // Remove the parameter

                lstrcat(pos, _T(" "));
                lstrcat(pos, url);
                result = (HINSTANCE) WinExec(key,SW_SHOW);
            }
        }
    }

}