See the RegisterHotkey()
] function in the MSDN and read the remarks. The second
parameter must be different for each defined key. You are passing uninitialized values which are probably set to zero by the compiler resulting in identical IDs.
To resolve this, pass different IDs:
RegisterHotKey(hWnd, 1, MOD_WIN, 'S');
RegisterHotKey(hWnd, 2, MOD_WIN, 'A');