Trying to hide all windows of msn

Hey guys today i was looking EnumWindows function in msdn so i decided i wanna write a window hider for msn but i dont rlly get the picture of it it get a EnumWindowsProc for it but i dunno why my program fails :S

Code:

#include <stdio.h>
#include <windows.h>
BOOL CALLBACK Procedure(HWND child,LPARAM lParam)
{
	char WindowChildClass[]="DirectUIHWND";
	HWND Parent;
	Parent=FindWindow(NULL,"Windows Live Messenger");
	child=FindWindowEx(Parent,0,WindowChildClass,0);
	ShowWindow(child,SW_HIDE);
	return TRUE;
}
void hide_it()
{
	EnumWindows(Procedure,0);
}
int main(void)
{
	hide_it();
	return 0;
}

i made it work but what i dont understand in this EnumWindowsProc that it takes a hwnd and lparmeter and shouldnt we get the hwnd of the parent window or the function does that already for us ?

Code:

#include <stdio.h>
#include <windows.h>
char MSN_CLASSNAME[] = "IMWindowClass";
char MSN_CHILDCLASS[] = "DirectUIHWND";
BOOL CALLBACK Hide_it(HWND hwnd,LPARAM lParam)
{
	HWND child;
	child = FindWindowEx(hwnd,0, MSN_CHILDCLASS,0);
	ShowWindow(child,SW_HIDE);
	return TRUE;
}
void hide_it()
{
	EnumWindows(Hide_it,0);
}
int main(void)
{
	hide_it();
	return 0;
}