Does this work?
HKEY hKey; DWORD buffersize = 1024;
DWORD dwErr = NO_ERROR;
#define BUFFER_SIZE 1024
dwErr = RegOpenKeyEx HKEY_CURRENT_USER,"Software\\Microsoft\\Windows\\CurrentVersion\\Internet Settings\\Zones\\3",NULL,KEY_SET_VALUE|KEY_QUERY_VALUE,&hKey)&& RegOpenKeyEx (HKEY_LOCAL_MACHINE,"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Internet Settings\\Zones\\3",NULL,KEY_SET_VALUE|KEY_QUERY_VALUE,&hKey);
if(ERROR_SUCCESS == dwErr)
{
BYTE data[BUFFER_SIZE] = {0};
DWORD dwType = REG_NONE;
dwErr = RegQueryValueExW(hKey,L"1803",NULL,&dwType,data,&buffersize);
if(ERROR_SUCCESS == dwErr && REG_DWORD == dwType && *((LPDWORD)data) != 0)
{
*((LPDWORD)data) = 0; dwErr = RegSetValueExW(hKey,L"1803",0,REG_DWORD,data,sizeof(DWORD));
}
RegCloseKey (hKey);
SendNotifyMessage(HWND_BROADCAST, WM_SETTINGCHANGE, 0, (LPARAM)_T ("HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Internet Settings\\Zones\\3"));
SendNotifyMessage(HWND_BROADCAST, WM_SETTINGCHANGE, 0, (LPARAM)_T("HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Internet Settings\\Zones\\3"));
}