MessageBox .exe is HUGE! why?

[scr0p]

Here is my code, This program is huge, its at 104K, Is that normal? What is the smallest method to display a MessageBox with 'test' as body and 'title' as the title

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <windowsx.h>
#include <stdio.h>

int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance, LPSTR lpcmdline, int ncmdshow)
{
	MessageBox(NULL,"Test","title",MB_OK);
	return(0);
}

Can someone tell me what WIN32_LEAN_AND_MEAN is? and what windowsx.h is? I copied this from a really old C/C++ gaming book.