I've been able to set local hotkeys like this
RegisterHotKey(hwndDlg, 100, MOD_ALT | MOD_CONTROL, 'S');
How can I set the hotkey to be global? I want it to be there even when my window is hidden.
I solved it myself but thanks for your reply here's what was wrong...
ShowWindow(hwndDlg, SW_HIDE);
RegisterHotKey(hwndDlg, 100, MOD_ALT | MOD_CONTROL, 'S');
if you register the hotkey first then hide the window... it ignores the hotkey for some reason... oh well.. it's working now :)