How to stop background thread

Usually, you set up some kind of inter-thread communication in your thread procedure.
For instance, if you're using PostThreadMessage():

DWORD WINAPI ThreadProc(LPVOID pX)
{
    // Cast passed pointer to what it really is.
    if (pX != NULL)
    {
        X *realPointer = reinterpret_cast<x> pX;
        // Initialize COM
        // Generate message pump
        ::PeekMessage(whatever);
        // Connect to database
        while (!done)
        {
            ::GetMessage(....)
            switch(msg.uMsg)
            {
                case WM_COMMAND: // Cast LPARAM to pointer to a Job, execute that job.
                    realPointer->ExecuteCommand(msg.lParam);
                    break;
                case WM_QUIT:// This is your cue to exith the thread.
                    done = true;
                    break;
 
            }
        } // while
        SetEvent(realPointer->reallyDone);
    } // if, scope for casted pointer.
    return 0;
}
</x>

In any case, the server thread and the client thread must be able to communicate. Google for 'thread design patterns'.

If you're using 'shoot and forget' threads, you can kill them violently, but this is a bad thing. Your best option, depending on your actual circumstances, may be to hide your main window, and just wait for all threads to complete execution.

Hope this helps,
Pablo.