Alt (menu) key

BOOL CMainFrame::PreTranslateMessage(MSG* pMsg) 
{
    // in full screen mode, ignore the Menu key, so we don't go modal
    if (pMsg->message == WM_SYSKEYDOWN && pMsg->wParam == VK_MENU && m_IsFullScreen)
        return(TRUE);
    return CFrameWnd::PreTranslateMessage(pMsg);
}