64 Bit Message Box Assembly

.586
.model flat, stdcall
option casemap :none

include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
include \masm32\include\masm32.inc
include \masm32\include\user32.inc

includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\masm32.lib
includelib \masm32\lib\user32.lib

.data
    MessageBoxTitle     db "Hello!", 0
    MessageBoxContent   db "Hello, World!", 0

.code
start:
    invoke MessageBox, NULL, addr MessageBoxContent, addr MessageBoxTitle, MB_OK
    invoke ExitProcess, 0
end start