Re-assign/override hotkey (Win + L) to lock windows

Question

Is it possible to re-assign the Win+L hotkey to another executable/shortcut?

Use-case - I would like to switch off the monitor of my laptop as

Answer 1

The Win+L is a system assigned hotkey and there's no option to disable it. This means there's no way for an application to detect it, unless you use a low-level global keyboard hook (WH_KEYBOARD_LL). This works in XP SP3; haven't tested it in Vista though:

LRESULT CALLBACK LowLevelKeyboardProc(int code, WPARAM wparam, LPARAM lparam) {
    KBDLLHOOKSTRUCT& kllhs = *(KBDLLHOOKSTRUCT*)lparam;
    if (code == HC_ACTION) {
        // Test for an 'L' keypress with either Win key down.
        if (wparam == WM_KEYDOWN && kllhs.vkCode == 'L' && 
            (GetAsyncKeyState(VK_LWIN) < 0 || GetAsyncKeyState(VK_RWIN) < 0))
        {
            // Place some code here to do whatever you want.
            // ...

            // Return non-zero to halt message propagation
            // and prevent the Win+L hotkey from getting activated.
            return 1;
        }
    }
    return CallNextHookEx(0, code, wparam, lparam);
}

Note that you need a low-level keyboard hook. A normal keyboard hook (WH_KEYBOARD) won't catch hotkey events.