How to disable normal behaviour of Alt key?

Question

Normally the Alt key opens the menu in Windows.

I need this to be disabled, because I need Alt key for my application. (It is an emulator of old computer, so I need to m

Answer 1

How about checking for WM_SYSCOMMAND, and when wParam is SC_KEYMENU, return 0?

Update / exact solution:

if(wParam==SC_KEYMENU && (lParam>>16)<=0) return 0;
return DefWindowProc(hwnd, message, wParam, lParam);

Description: If lParam>>16 is positive then menu is activated by mouse, when it is zero or negative then menu is activated by Alt or Alt+something.